i'm thinking about making my own model sub with static ballast and i was wondering where i could find small pumps? i'm looking for pumps about the size of a "C" cell battery if not smaller. they need to be reversable and be able to pump to maybe 1 bar pressure. the pump doesn't even need to make a good seal as the pump can constantly be on in order to keep the ballast tanks full of water. any place i can find something like this?