LIP-4WM genuine Sony 'Gumstick' (Sony LIP4WM, Sony LIP-4WM) 370mAh Li-Ion. Audio battery.
My first LIP-4WM build - and it works!, yay! : r/minidisc
Sony LIP-4WM Battery for MZ-NH1 for sale online | eBay
LIP-4WM Lithium ion battery Substitute | eBay
Your Sony Hi-MD player deserves longevity. These lip-4wm compatible battery is your answer. They are also 500mAh vs. 370mAh (original Sony). The search is finally over. Selling for €20 plus shipping. Shipping
MiniDisc Obsession — Hallam Inventions
2023 NEW 500mAh LiP-4WM battery for sony RH1 EH1 NH1 NH3D NH1 MJ97 HMD - AliExpress