Keep a copy of it in your records, should a problem ever arise. As long as he keeps his end of the contract, you shouldn't have to think about it again.
I already gave you two resources. They're the only ones that came to mind. You could just do a google search to find a free template, but I probably wouldn't trust any found that way - stick to ones created by legal professionals. Nolo would be the best option I can think of, but you probably have to get a whole book.
Just go to www.allbusiness.com or www.nolo.com. If nolo has one, it will be inside a book - not directly on the site. If allbusiness has one (and I don't know if they do - I only know they sell paid templates), you should be able to buy it on their site.
Here's one from a company that I have heard positive things about, it will cost you but it's much cheaper than hiring a lawyer and the document was written by lawyers. http://www.legalzoom.com/legalforms/Mutual_NonDisclosure_Agreement.html
The most important single element of any non-disclosure form is making sure that you describe what is being treated as confidential. With any standardized form, you run an increased risk that the description is either too narrow or too broad. Make sure you know what you are doing if you use a form you just grab from somewhere. The fact that a form "was written by lawyers" is not helpful unless it was written by lawyers with your situation (or a similar situation) in mind. I have written many contracts that were good for the use intended but could be a disaster for someone with slightly altered circumstances.