Well that is cool. I guess if you are not storing your A2000 for too long and use it regularly that's not too bad. I have two A2000's and sometimes because of space, I have to stick them in the closet in between uses. I have been using these cordless phone batteries
The Amiga can charge them after some time. They last a very long time in storage, months. You can also buy the mating connector on eBay for a few cents but I just cut the connector and solder some jumper connecters on wire pigtails and then solder pins to the battery holes on the motherboard. This way I can easily unplug the battery and the wires are long enough to velcro or zip tie the battery to the front of the chassis, out of the way of the motherboard just in case.
Of course it is probably easier to just use a CR2032 and a holder with a diode and be done with it, I like to complicate things.