rebuilding factory solar collector

I recently bought 3 used 4x10' flat panel collectors. Glass glazing with Copper tube copper absorbers. I am adding to my existing solar sytem. These were factory made but no labels are on them. After pressure test and repair , (they overheated on last guy) I am ready to put back together. Question is, does any body know where I could find the rubber gaskets (shape of seal is U formed with hole for 1"coppper) which go on each corner of the collector where 1" copper exists panel on side. I could rig up a new seal and gob up some silicone etc, but a facotry type seal would be best. thanks