Pretty big market really so I guess it depends what kind of features you're after.
Just a wearable player with a rudimentary interface, maybe something like the Sandisk Clip Sport Plus. It has Bluetooth and microSD slot for expanding capacity:
https://www.amazon.co.uk/SanDisk-Cli.../dp/B01LW2F237
The Sony NW-A35 is a really nice Android based player but it's nearly 200 quid:
https://www.amazon.co.uk/Sony-Resolu...01NCTHCG7?th=1
There have been a lot of plaudits for FIIO and Cowon music players but as far as I know they lack Bluetooth and imho the build quality is questionable: cheapo Chinese junk syndrome.