Hoofie;
Rectifiers are rated for volts and amps. I suspect you can use anything rated for the same values as the original and be fine. How old are these things?
I probably have some diode packs that would work but without knowing if it is just a single rectifier or a bit more complex it is hard to say..
Finding that style is unlikely but you can wire in other components and it should work. Got a photo of how it is installed?
If I had time for IRC I would tell you to pop in and we would sort it out but I don't get on live much lately. Others could help there, too, I am sure.
Simple answer:
I think we could make them work again. Assuming all that is wrong is the rectifier. We could figure that out for sure pretty quick on IRC, too.
Tom