Searching for OTICON OPN S 3 RECHARGERABLE BATTERY DOOR MODULES (ZBDM-01) both left and right door modules. Can be reached on this site or email me at skua97@yahoo.com.
A → DIY School Hearing Aids PDF file named (Li-ion Rechargeable Battery History) provides some historical information about the turnkey solution from ZPower which includes a cautionary warning about (Silver-Zinc Rechargeable Battery) problems and the warning is from ZPower (themselves). Just wanted to mention that warning/issue (see clip below).
But now that ZPower is gone, I don't know of any place to get the battery-door-conversion-kits. I don't see any on EBay which would seem like the obvious place to look??
Clip from (Li-ion Rechargeable Battery History);
ETA: Thanks for asking this question. It prompted me to do a slight re-write of this DIY School Hearing Aids PDF file (Li-ion Rechargeable Battery History) to say that the turnkey solution from ZPower is obsolete. Previously this PDF file said it was going obsolete.
It looks like riotenergy.com took over the production of the ZPower batteries size 312 and has been selling them officially, although they're out of stock at the moment. But they don't seem to be OEM'ing the whole ZPower systems to HA mfgs anymore. They're probably just selling the battery replacements for existing systems.
I think the only source you can find parts for the ZPower system now is from eBay.