My level of electronics is very rusty but I think you could just add mosfet. It has 3 legs one is signal that when on tells power to flow trough the other two pins. They can easily go upto 8amps and will cost you around 2bucks a piece. You will need several but I don't know the specifics. You should think of them as an amplifier.
hope i helped a bit
hope i helped a bit