Wallstreet used 6 batteries total, all 2330 50mA each rechargeable lithium.  They were arraigned: 3 batteries in parallel with red wire to + side. White wire to the - side. Second set of batteries are also in parallel with the + side connected to white wire and - side of first set. The black wire connected to - side of the second set.

red and black are probably the main wire for recharging and for maintaining PRAM. White wire may be for reference when charging the battery.

You could replace it with any lithium rechargeable.  I've planned on 2 more common regular lithium batteries wired the same way but instead of putting it into the tiny compartment, I'm going to hot-glue it in where the large battery pack normally sits.  I have gutted the dead battery pack so I could trim one end to make room for the new PRAM battery and put it in and make Wallstreet look complete.  I'll do pictures when I get the new battery in, Wallstreet is a pain in the butt to change PRAM.

I also need to do the same thing with my Duo 280c (2 battery cells, same wiring design)