Just rebuilt my spare distributor. The o-ring on the mounting face was flattened and hard, so I dug it out. Now I can't find a replacement at the usual suppliers.
Is there a supplier? Is there a commercial o-ring that will work?
Go to any well stocked hardware store. I am sure that you will be able to find something suitable in the large selection of "O"-rings most good stores carry.
A while back, Bubba was giving these away for free. He mailed out two o rings to those who inquired. I'm working in the garage, if I find them, you are welcome to one. I'll DM you when I find them.