Joe,
I have the links on another computer, but there are sites that will allow you to download cad files of many and varied parts. They are mainly standard engineering parts there are a few model cars trains and aircraft and who knows some hands and other body parts.
I know similar questions have popped up earlier so a search of this forum if not a general web search should help you to find the sites.
Also do you need a visually realistic hand or a crude looking but ergonomically accurate one. I may be able to find elements of the later.
Best Regards
Hudson