You can even go to Radio Shack... get a 4-cell AA holder and use off-the-shelf AA Alkaline cells (which would give a couple f flying sessions per set) That is what used to be the normal RX pack before the NiCds became common. (gets expensive replacing batteries all the time)

The AAA size battery holders will work for the TX. (the AA holders won't fit in the TX) NOTE: If using alkalines you need to use a dummy cell for one cell in the TX 8 AA Alkalines will be too high voltage for the TX.

Radio Shack also sells some Cell phone, cordlerss phone and other type pre-made NiCd packs. Some of these are pretty good for RC use. You are looking for a 500 to 700 mah 4.8 v "nominal" pack. You can use a smaller capacity but you get less flights per charge. (I used a Radio Shack 250 mah cell phone pack to save weight in a model powered by a .25, and got 3 flights (4 oz tank) per charge.

Unless you are GOOD at soldering... you don't want to try soldering together your own battery pack. I have a friend that solders up packs from Ray-o-vac NiMh cells from Wal-Mart. $1750 to buy the 8 cells to get a 2100 mah TX pack, and we are using leads taken from old computers. (the LED leads fit the swithc harness and are heavier wire than the original battery leads.

There are PLENTY of options other than using old, unreliable batteries..