Adam,
According to the manual, that's a 3.6V 60mAh Nicad battery. I think I'd avoid getting anything much larger to avoid damaging the charging circuitry in the Amiga. Oh yeah, a neater way to mount a replacement battery off-board is to run the wires through one of the vent holes in the metal front of the 2000 frame. (after removing the case top) just stick the battery to the frame with velcro. The top cover hides the hack neatly. :-)
