This website sells IB4200WC Packs for a good price.
http://www.boomboombatteries.com/Sea...ults.asp?Cat=4
This website has a review of some of their IB3800 packs
http://www.beatyourtruck.com/prodreview-IB3800.html
I have one question though, why not go lipo? You have the 989 charger, so you can charge lipos already. Flightpower sells some 2s1p 3700mAH packs that I think would be great for stock racing. Although they are $90 apiece, they should be MUCH better than any NiMh pack.
Just my $.02
Brad