20 year old "Overhead Door" brand opener and the sensors have stopped working. Only closes with the wall button held until closed. I've read the posts and probably need new sensors.

1. Where do you find Overhead Door parts? I've tried before, locally for a remote or a lens cover, and they were no help.
2. These HAVE to be compatible with another brand, but have never found that information. Lots of sensors out there, on the web, but nothing about OD brand.