vhbw Replacement Battery compatible with Sony MZ-B3, MZ-E3, MZ-R2, MZ-R3, MZ-R30, MZ-R35, MZ-R4 Portable Mini Disc Mini DV (2200mAh, 3.6V, Li-ion): Amazon.co.uk: Computers & Accessories
Kastar 6-Pack 7/5F6 1.2V Ni-MH Battery Replacement for Sony NH-9WM NH9WM NH-9WM(N) WM-EX612 WM-EX622, Sony D-EJ1000 MZ-N710, D-EJ01, D-EJ2000, D-EJ825, D-EJ885, D-EJ915 Portable CD/MD/MP3 Player - Walmart.com