I'd consider posting an ad for the PCB, I've seen several go through the sale forum. I sold one some time back from a command upgrade of the dockside switcher.
Another option might be to swap out the board and stick an old LionChief board into it. You can buy a variety of boards and matching remotes from Lionel parts, they're not that expensive. You'd also have remote control and better sound.
Finally, there are lots 3rd party reverse boards that would fit in there and return it to functionality.