LiPo's work just fine with a regulator, no problems with that...


However as CGRetired pointed out, if you do not already have them on hand, ( and it sounds like you do not... ) then you are also probably missing chargers, and the other items you need for their care and feeding...

As such it would be easier and cheaper for you to get a replacement but higher capacity NiCD or NiMH pack that you could charge with a standard wall wart charger.