I know I did, so I finally got tired of wishing at the well and just up and made one. Unfortunately, I didn't take pics of the steps, so some things are going to be represented by simple drawings (they'll be easier to get the gist of, anyway).
The nifty part about this one is that no one but you and your wizardly hand can activate it, because you are wearing the power source in a pocket or sleeve, with the wires running to a pair of rings, one positive and one negative, on your fingers. You *must* wear them with at least one finger between them, so you don't short out your battery pack. :-) It's perfectly safe, as long as you don't forget you're wearing it and grip a metal post for very long (it'll damage the batteries and overheat them), because you're only dealing with three AA batteries in series.
What you'll need to make one of these:
A small battery powered (or USB-powered) plasma ball. I got mine for less than $5 at http://www.geeks.com quite a while back along with a number of other "useless" toys in their clearance section, but they don't seem to have them anymore. http://www.thinkgeek.com/homeoffice/lights/964e/ does, though they sure cost a bundle (it's exactly the same as the one I had, from the pics they show). Betcha you can find one cheaper.
Some clear, some black and some white silicone sealant (buy one tube of each if you have none yet). I use this stuff a fair bit, so I get it at Home Depot in the cartridges for those grease-gun style tools, though I rarely actually use the gun to apply it; I squirt some out on a cottage cheese container lid and then use various tools to apply it to the surfaces in question.
A suitably gothic, wizardly, or at least halloweeny looking cup that's at least a few inches deep, andjust a bit smaller than the diameter of the glass globe of your plasma ball. I used one from a cheap set of plastic halloween party cups found at a Fry's grocery store some time back, kind of like the one in the images below. I couldn't find one online to link to, but you can likely find something suitable anywhere you look right now.
Some copper wire. Preferably lots of unininsulated stuff, For mine, I ended using mostly wire out of an old vacuum cleaner cord that'd been chewed up by a dog. I stripped the entire length of all three wires of all insulation, and got quite a lot of thick stranded wire.
A 3-AA battery holder, preferably with a goodly length of wire attached. Radio Shack sells them (well, many still do) at an exorbitant price, but you can possibly find them in things you already own. If you want a little brighter light, use a 4-AA and put a diode in series with one wire to a ring., to cut the voltage down to prevent possible damage to your nominally 5V-powered plasma ball.
Some insulated cable with two wires (like speaker wire), or simply twist two separate insulated wires together . Make sure to use something with two different colors so you can easily tell positive from negative.
A couple of cheap brass rings that fit the fingers of your staff-holding hand on either side of the middle finger. They don't have to be brass, as long as they're conductive and look spiffy for a wizard to be wearing. It's better if they are a solderable metal, and acquired just for this project, so you don't have to worry about the power wires coming loose while you're dressed up.
A cool-looking knurled stick . Or whatever suits your style for your wizard staff itself. Make sure it's something you can hack into a little bit.
If you have leather or fur scraps around, these can be used not only to add ambience to the stick, but to make a carry bag for plasma globe guts if they won't fit in your chosen cup.
For tools, you'll need the common electronics manipulation tools of:
Soldering iron and solder
small screwdriver set
I recommend having a dremel and bits handy, but they're not required if you are creative with other tools, including utility knives and the like.
Some tools you might find needed that aren't listed here, depending on your choice of staff materials and the like.
In the pics, you can see the light even in a lit room, but barely. It works way better at night:
Sorry the video is sideways, for some reason the camera would fade in and out if I videoed it the other way--something wierd in it's autoiris, I guess.
Step 1: Take apart the plasma ball
However, it's highly likely that yours will have a few small philips screws holding the base cover on. Undo those, then carefully remove the cover plate.
Inside will be the electronics for the plasma ball, which may have very long wires or very short ones. Mine had long enough ones to move the entire PCB more than a foot away from the ball! Yours may not. If you don't have long wires, you're going to have to have room inside the cup under the ball to secure the PCB.
I didn't have that kind of room in my cup, but since the wires were long enough, I siliconed the high voltage areas of the PCB to prevent electrocution, and let that cure for an hour or so (long enough to get a good skin on it), as I was in a hurry to make this for a party. :-) While it was skinning over, started work on the rest of it.
The globe is delicate, so be careful while handling it, especially where the nipple comes out at the base. This is where the red HIGH VOLTAGE wire on mine attached, simply by friction-fitting the stripped-bare wire as a little bundle inside the recess in the middle of the ball's base. I simply gently pulled it out, and set the bulb aside to begin attaching it to the cup in a little bit.
On mine, it had a standard little DC input jack for 5V, and a cable that came with it converting that to a USB device cable. I didn't need either, so I unsoldered the DC jack and simply spliced the wires that had been on it to a pair of red and black wires about 2 feet long. Those are going to go to the contacts down around hand-height on your staff later. I saved the other parts (and the plastic base and such) for later, as I am sure I will use them for a different project. :)