I would also look at the
6400mah packs @ TrueRC. Make sure you get the 45mm wide ones.
I have a pair of these in series (for a 4S saddle pack) and they are really nice for the price. If you ask I'm sure he could make them into a 4s2p pack as well (or just make your own y cable.)
They are $80 for a 2s2p pack. I'm using them now in my basher Revo and I'm very satisfied. I get ~25min or so of speed runs, but ~1hr bashing around. The 30% extra mah in trade for a couple hundred grams is worth it IMO for a basher.
Edit: Also the
4S2P 10C 8000mah pack for $140 is not bad as well for a cheaper pack. They are 50mm wide tho, so it may or may not fit the chassis depending on how you converted it. My 5S config uses these cells and they have tons of power, even for just a 10C. Something to consider for a low cost basher pack w/ lots of runtime.