I'm sure you can find a good sample contract online. But if you just sat down and thought about it I'm sure you could come up with one just as easily.
The person who wants to take the contract needs to know things like, what do you want them to do, how long do you want them to do it, and how much money are they going to get paid. As the person giving the contract you are going to want to know things like what happens if the item isn't as good as you expect, or what happens if it takes longer than the deadline. Stuff like that.