I would suggest looking around the neighborhood at old/unused BUD dishes and talking the owners out of the dish and using the polar mount from it and modifying it to your project. However, you may then decide to keep the BUD instead.
It seems like you should be able to mount, say a 1.2M dish on a C-Band mount or something like it.
I've been thinking along those lines, but am still puzzling over the mounting of the offset dish since the mounting point would be in a different location than a C-Band dish.
It would be an interesting contraption to mess with.