Looking For A Sitter I Can Call Whenever Needed

I'm looking to find sitters I can call whenever I need someone to watch my son. There aren't specific dates, I'm hoping to find a few ppl I can call if and when I need a sitter. My son will be 5 in February, he is level 3 autism spectrum disorder , technically non verbal but he does talk and has his ways of getting what he needs. He attends pre school monday-friday, he takes a nap after school, he is also still in diapers. His father lives with us but I am his main care giver. He plays well by himself but still needs to be watched all the time so I am never able to get anything done, or do anything In general. I'm hoping to be able to get some time to myself to get things done or to just visit a friend.