I've been using [this model](https://www.amazon.co.uk/dp/B084TLDWVQ/ref=cm_sw_r_apan_glt_fabc_SVVW2F3YRM5MD5C3S8R4) for years.
Quite cheap. Bluetooth, radio.
Most importantly for me, it has microsd slot. I have a 512MB card that contains my favourite songs, so I can leave my phone at home and focus on my workouts at the gym.