Late to this thread but Trainz has Lionel part 6208613103, the reverse unit for the Docksider, in stock for $23.99. See https://www.trainz.com/product...e-unit-pcb-docksider.
swede
After posting, I tried the link and it didn't work. I then went to the Trainz website and searched for "Lionel 6208613103 Reverse Unit PCB /Docksider" and was able to get to the proper ad.