The pre-made one Serpent has (801173) is pretty low amp (730 mAH). Mytsn staes it's for the 705/835 but the 710 uses the same one.

I suggest if you can get the newer GP (950 mAH) or Sanyo (900 mAH) AAA cells, then make one or ask someone else who could do a nice job on it. I prefer spot welding them if you can.

Or try ebay for a good price.