Dave, thanks for the kind words. Barry & I sometimes disagree on details, but you will never get bad advice from him.
I'm sure R-S did not manufacture anything, which means that somewhere those power supplies are still available. Googling will probably turn up a source, and it will probably be cheaper than R-S. Also, there are many power supplies available from outfits like Digikey, Mouser, & Jameco. Since the TIU is fairly flexible on input voltage to the AUX port, these possibilities are worth checking. Without AIUs, I'm willing to bet that using one R-S will handle both TIUs. There is a two-fold test: (1) Does everything work? (2) Dies the power supply transformer get too hot to the touch?
For the general benefit of forumites, I have heard that these plug-in wall warts are a frequent source of house fires. I was in the Brunswick RR Museum once, and smelled hot rubber. The attendant and I searched, and eventually found that the plug in for a telephone was red hot.
