Timmahh

YES, there are, as stated JR makes one to fit in. its about 50 bux, and is 700mah.... heres what i did, available at your LHS or at Tower Hobbies.
i went to the bay and purchased rechargable DURACELL AA @ 2500 mah rating, then you get some wire, the approrpriate end needed, some small metal strips, heatshrink and a soldering iron...
1 solder 4 negative ends with small metal strips to connect the 4 neg sides, add a piece of wire. preferably black to idicate negative.
2 do the same to the positive side of the other 4 batteries. adding a wire, preferably Red for positive..
3 put a piece of HeatShrink around the Negative end of your batts and light shrink into place. do the same to the positive side, but cut a hole in the middle of this end and pass your wires thru.
4 now cut a piece of Heat Shrink long enough to put all the batts into, and heatshrink it to the bottom of the battery pack, befor you do the top side you need to make sure your pack is aligned correctly and all batts are firmly together in the middle to make good contact. then continue to shrink it all together..
5 cut your wire leads to an appropriate length and add your end and voila.. a 2500mah rechargable battery pack..
the trick with JR is they have their wireing reversed. so if you get it done, and your TX wont power up. swap your neg and positive lead at the connector... but you should be good without doing that....

hth
Timmahh



battery line up... i will use simple keys to illistrate here.

______ ______
-[______]+-[______]+______+ this represents all the side views of your batt pack
-[______]+-[______]+
________________________-


your bottom and top view will be simply OO positive on top negs on bottom.
OO