Just throwing this out there, and I don't know if it will help you but I seem to recall seeing a "finger tip stylus" for the Nintendo DS a while back. I never used it myself but it definitely doesn't require you to hold anything so I thought it might be an idea. I don't want to link to any specific product since I haven't ever used one but just google for "ds finger tip stylus" and you'll find what I was thinking of.