JonR's suggestion is the one I was thinking. You can make any kind of "jumper" with different plugs on each end to mate up two different connectors. Once you have finalized your system you could take the extra step of cutting off the old plug and replacing it with a compatible one or just continue to run it with the jumper. With a DC system (batteries) you just have to make sure you get all the positves together and all the negatives together. The light bulb doesn't care, but the switch might, or it might not. Just test your connections to make sure everything works before doing anything final like soldering.

I'm holding out for Allister's 10-LED system!