I purchased Panasonic Eneloop AAA rechargeable batteries ($6.95 4-pack on Amazon). This repair was quite simple and the guide is perfect. I had no issues with performing the battery swap. The only issue I had; I did not have the electric package seated fully, just make sure you press it fully into the cavity.

TIP: one trick to soldering to batteries. Use a fine metal file and just rough up the surface of the battery contacts. just want to take the shine off of them with the file. They will take solder without issue and little effort. The bonus is you can place the solder perfectly in the location you want it to stay.