If you're able to find a Rockbox compatible player you can add bluetooth capability. This is what I assembled:
Sansa Clip Zip with Rockbox v3.13, MPOW BH283A bluetooth receiver/transmitter, Taotronics TT-BH16 bluetooth earphones, optional PortaPow 3400mAh battery pack. Works well.
I'm not sure the max card size for Zips.
Edit> I was way out with my earlier recollection of battery life. Tested the batteries today from fully charged and at moderate music volume to empty: bluetooth earphones 6hrs (including final 1hr with 'battery low' audio warning every 5mins), MPOW 8hrs 27mins, Clip Zip 11hrs 3mins. External battery pack not used. The Zip is over 10 years old - not too bad.
