I found an aftermarket one in a local store: https://www.akku-elem.hu/Utangyartott-BIOS-elem-02K6486-200mAh-3V-Li-ion https://www.akku-elem.hu/Utangyartott-BIOS

I found an aftermarket one in a local store: https://www.akku-elem.hu/Utangyartott-BIOS-elem-02K6486-200mAh-3V-Li-ion https://www.akku-elem.hu/Utangyartott-BIOS-elem-02K6486-200m... (I think they make them themselves)