Mark,
Either that, or do what I did. I got a 10 amp full wave bridge rectifier from Radio Shack a while ago. See the attached photo with the dime for size comparison. Since they're not found much any more, I'm sure there are other suppliers out there. I made a small "project box" with AC inputs on one side and the circuitry inside which included a DPDT slide switch for reversing polarity. The other side of the box had two terminals which goes to the track. And because I like to complicate things, I also have a DPDT switch on the box that allows me to select AC or DC output. I hook the box's input up to one of my Flyer 13B or 18B transformers, which gives me plenty of leeway in the power department.
The nicest thing about running DC is that you can reverse the locomotive when you want, and not have to go the F-N-R cycle that a the reverse units make you go through. But if the loco has a DC motor, it's mandatory to use DC, like my 332 Northern which pulls 5 illuminated heavyweight cars easily. It's also handy for any other DC locos that I have.
