If the switch is indeed low voltage and the contact resistance is the problem you could simply twist the wires together under a wire nut to test the circuit without a switch.

If a standard 120V single pole switch has too much contact resistance you might try a high quality DPST (double pole single throw) switch and tie both switch poles together to half the effective contact resistance. With the cover on it would look the same.

Or, go to Radio Shack and buy a high quality toggle switch which will have either siver or **** contacts.