If you have assess to some metalworking tools you can make a cable release that can be adapted to any digital camera. The cable release (with locking collar) can be bought at on-line auction sites for under $5.00 each.
Step 1: The Adapter Bracket
The bracket needs to be reasonably rigid, but a bit of movement won't cause a problem. There are no dimensions for the bracket because every camera will be different. I have 3 digital cameras, but my bracket only fits one of them. If you need to use the cable release with more than one camera, simply make additional brackets.
Make the bracket to suit your camera, and drill the 7mm hole first. Then make up the nut assembly and attach the bracket to your camera. Now, carefully mark the hole position for the cable release - it must be positioned exactly above the shutter release button, so when the remote thumb-press is pushed it will take a photo. I can't give dimensions for this because it depends on the camera.
You can see all the relevant parts in the photo. The hole for the camera attachment nut should be 7-8mm diameter - sufficient to allow an easy clearance for the 1/4" threaded stud. I have no idea what the thread on the cable release is (it's tapered, so size is irrelevant). I found that it will screw into a 3mm tapped hole perfectly, so the small hole should be 2.5mm and tapped with a 3mm ISO metric tap.
The attachment 'nut' is the only part of the project that might be a little difficult - especially if you don't have access to a 1/4" Whitworth tap. A metal lathe is useful, but not essential, and even if the hole in the nut is a little off-centre it will still work perfectly.
Step 2: Attachment Nut
The easiest way to create the internal and external threaded sections is to simply drill out the centre of the aluminium (or brass, or even hard plastic) and tap it all the way through. A short length of 1/4" threaded rod (cut from a metal thread screw) can the be screwed into the 'nut' and secured with a grub screw or epoxy.
The correct drill size for 1/4" BSW is a Number 9 drill (from the number series). The recommended size is actually 5.1mm, but a standard 5mm drill works fine. The end of the nut with the tapped hole should be recessed slightly (about 1-1.5mm, as shown in the drawing) because some tripods and camera stands don't have a thread that goes all the way to the mounting plane.
When drilling or tapping aluminium, always use a lubricant. Methylated spirits (denatured alcohol) is ideal but possibly dangerous, or you can use WD40 or any other 'water displacement' spray. Make sure that you clear the chips, or you will break the drill or tap, and NEVER hold small pieces being drilled in your hand.
If you use a grub screw as shown to secure the metal thread in the 'nut', make sure that you file a small flat onto the metal thread where the grub screw will hold it. This ensures that the metal thread cannot turn as you tighten it into the camera.
You now have a cable release that defies the camera makers' objective of not allowing you to do so. You'll find it invaluable for extreme close-up shots, as well as night photos where you need a long exposure and the smallest camera movement would ruin the shot. The ability to use 'bulb' time exposures depends on the camera, and I can't help you with that.