You didn't mention quantity needed, but you might want to contact Ovonic Battery Company in Troy, Michigan. They are involved with HEV pack development using NiMH battery chemistry. You can reach their website at
I did make a request to them an while ago but so far no response from them. Do you by any chance know anything about Exide's molded lead-acid battery that each has cooling ports for coolant to flow in? It seems no members from Exide in the US know anything about it, but yet it was shown in the car show in Germany last year.