https://www.amazon.com/gp/product/B09K7L1P78/ I use this one, it's been working great so far. I charge it for about half an hour every couple of weeks. It was around $16 when I bought it, you should be able to find them for under $20 from some seller, check reviews. There are also little "washing machine" style ones for very cheap with a pull string or button that are supposed to be good too (haven't tried them), but I think they end up using a lot of multipuropse solution so maybe false economy.