Have you solved your problem?
If not and if you are only looking for something for the car, does your car's entertainment system have a USB input? You might want to keep a USB stick just always plugged in and you an have everything you want with you. Car entertainment systems are notorious for being stupid about indexing music on a stick. Many will play the songs on an album in alphabetical order instead of album order. But that can be corrected using a drive sort software like drivesort.exe.
Of course a lot of people bluetooth their phones to the car now to play music. I don't like to do that but many people do.
If you are looking for something to play music though headphones while out and about, and don't want to use your phone, finding something good is a real challenge. The whole standalone music player market is pretty hollow. Many people use their phones now.
I did want a new portable music player because my 7th gen iPod Classic with the 160gb drive is now not large enough for my music and it's quite old and probably won't last longer. I also don't like bluetooth and didn't want another thing (headphones) to charge.
There is basically no middle market for portable music players. It's either really cheap stuff for $50 or very expensive stuff. I ended up getting a Fiio M11S
https://www.fiio.com/m11s . Excellent sound. Plays FLAC and ALAC as well as MP3 and AAC (M4a) . It has a MicroSD slot so space isn't a problem. My music library is now about 170GB. I also wanted to use wired headphones. It's a bit large and heavy. And none of these units have good battery life these days.
I really don't understand why no one can make something as good as the iPod Classic was anymore.