There will soon be a Lipo saddle pack on the market. There is a thread about it. He may be posting a picture of it this week. It's made by Gavin of Speedzone.
Team ORCA / ORCA USA / Pro Spec
Serpent America / Team Serpent S411 ERYX / On Point Racing OP12C, S120 / Xceed Products
Hangar 30 / Seattle RC Racers
Fasttrax Racing Series / NORA On Road Series