I can confirm from opening up my galaxy buds+ that the battery is NOT the same as those sold for the regular galaxy buds. The + instead use an EVE branded rechargeable battery which is bigger in diameter than those of for the regular. I found and linked replacements from AliExpress. Despite them being listed as 60mAh, the description below list them as 85~90mAH so I'm confident these are the ones.
US $9.99 | 1PCS ICR1454S ICR1454 CP1454 V1.0 battery capacity 60mAh Bluetooth headset smart bracelet smart wear
https://a.aliexpress.com/_mqMYR1Z