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.