Step 1: Parts and pieces
1 - Book holder. Barnes and Noble sold it for $12.95. It will hold paperback and hard cover books.
1 - 1/4-20 all thread bolt. I used a 5 inch long bolt but pick one that fits your stem.
4 - flat washers. Two sized to fit the bevel inside the stem, two sized to fit flush with the outside of the stem.
4 - 1/4 inch flat washers to help hold things together.
2 - 1/4 inch nuts.
1 - 1/4 inch lock nut to make sure it stays together.
All the hardware came from my neighborhood Ace hardware store.
1 - Dremel with a cut-off wheel and grinder bit.
1 - ratchet and socket(s) sized to fit your bolt and nuts.
1 - adjustable or combination wrench sized to fit your needs.
1 - bench grinder to speed up the correction of a marginal Dremel cut.
Total cost of parts: about $15.
Step 2: Prepping the stem.
After that, I used the Dremel with a grinder bit to put a small bevel on the inside of the stem to help the smaller flat washer center the post assembly.
Step 3: Assemble the post
The larger flat washer had a hole slightly too large for comfort so I added a 1/4 inch washer to keep the bolt from pulling through and to make it look a little better.
The assembly order for this end of the post is; 1/4 inch washer, large flat washer, small washer, 1/4 inch nut. Make sure the smaller flat washer is fairly well centered on the large washer. You could add a drop of lock-tite or something to the nut but I didn't think it was necessary. (Okay, actually I didn't think about until just now and I hope it's not needed.)
Slide the post into the stem and place the smaller flat washer over the bolt. It should be just barely above the edge of the stem, again to help with centering. If it drops below the edge it may end up too loose and you could have a rattle.
Center the larger washer, add the 1/4 inch washer and nut and crank it down tight. Again, lock-tite wouldn't hurt but I don't think it's needed. We'll see after it gets a few miles on it.
Step 4: Final assembly
One of the reasons I chose the book holder from Barnes and Noble is that it had a hole in it already, right where I wanted one. And it's made by our Canadian neighbors.
So, add the next 1/4 inch washer, the book holder, the final 1/4 inch washer, and the 1/4 inch lock washer. Tighten it up good and tight. It wouldn't do to have your book go sliding away would it?
The second picture is a look at it all put together.
Step 5: Installation
I didn't have enough hands to fit the stem onto the handle bar and hold the camera at the same time, (and your stem will undoubtedly be different than mine) so you'll have to figure out how to actually get it on your handle bar yourself.
My stem was stretched out enough that I needed a pair of pliers to squeeze it together far enough to get the screws started again. Once I did, it was a simple matter to set it at the right angle and tighten the screws up.
Step 6: Hey! It's done!
She liked this project so much that she said more than once she was "impressed". Better praise can't be had.
After spending a few weeks thinking about how I wanted to do it and finding all the parts and pieces, actual construction only took about 2 hours.
Just in case someone gets crazy: DON'T use this as a book holder in anything other than a stationary setting. I take no responsibility for you crashing and hurting yourself. Seriously.
However, I have a few ideas about how I can modify this to hold a GPS or video camera or something of that nature. I'll post any changes I make (I think).