I know what you mean.. mine's on its third battery from years ago. It's one of the extended size ones, even came with a new back cover for the phone because the original can't handle the thicker battery, but it's showing its age now. Used to go 4-5 days on a charge, now I'm lucky to get 2, and looking around there are still some places that sell them, but most of them are stupid expensive or a tad sketchy... or a little of both.

Yeah I really liked the s4 mini. It was a great form factor. It is a little slow these days but still works ok, I think I've got Lineage 17 built for it. I can still get batteries on Amazon for it? But the networks banned it so it's just a media device now.