Alright Guys I have fixed R6 by myself for about 12 USD as cost of new battery and shipping to me. I couldn't find original model 575593 anywhere. Even HiBy refuse to send battery alone because of shipping restrictions. I have checked space inside DAP and found in catalog that model 485780 may fit. Ordered on Ali here :
https://www.aliexpress.com/item/32917292817.html About 6 weeks of waiting and Today I have received it. Fits perfectly. My HiBy R6 is like new now. Battery life before was 2h at 2.5mm output with M1570 headphones. Now battery life is around 6h
Wonderful sound from this DAP !