Ali express (like Chinese Amazon, mostly direct from factories I think).

They are always "on sale", but the prices are usually 30-50 bucks.

Here's an example: https://a.aliexpress.com/_mOcxZJq they come with thousands of games that for the most pretty just work. It a game doesn't emulate well, like mario64 didn't for me, I don't know what you can do about it.

Get the r36S - the S is faster or something.