I think the main reason you're not finding anything with your approach is that in the event that a team needs someone to work a few extra hours a week in the ev

I think the main reason you're not finding anything with your approach is that in the event that a team needs someone to work a few extra hours a week in the evening, they hire someone they know personally, like former staff since they don't want to train someone who will only work a few hours a week. If you want to find work like that, my suggestion would be to pitch projects to companies. For example, "Hi prospective company, I'm using your iPhone app and it really needs an update due to x and x reasons. I specialize in updates of this type; here are some past examples of related work I've done. I think we can strike a deal that really improves the app at a price that makes sense for both of us."