regarding the Dia Compe centerpulls... those always struck me as some of the coolest centerpull brakes ever!
In the worst case, you could always just buy new cantilever brake shoes. With better luck, some of Kool Stop's replacement pads might fit. They make a few pads for Weinmann brake shoes, so hopefully Dia Compe copied the Weinmann brake shoe dimensions along with most of the other stuff? You could probably drop a line to Kool Stop and ask them, or at least you can check the dimensions of the pads on the Kool Stop web site.....
Kool Stop International - High Performance Bicycle Brake Pads Since 1977 (this is just one version of pads that fit Weinmann shoes)
Steve in Peoria