I drafted my own using several samples and then had them reviewed by an attorney. Laws vary between states and countries.
You can also join the Freelancers Union (an awesome resource in the first place and it's free to join.) They have a contract generator on their website. https://www.freelancersunion.org/
I still recommend having an attorney (in your state and in this practice area) do a review. The first time there is a problem, you'll be very glad you did.