I have several of Droll Yankees Onyx Clever Clean 12" sunflower feeders (CC12S). About 2 months ago I came back to one on the ground. They used to make a special seed tray for them (#CCT or CCT-S). The tray was broken and the plastic plug gone. The company got bought out in 2017 by Classic Brands (classicbrands.net) who also owns More Birds, Stokes Select, Squirrel-X in addition to Droll Yankees).
Anyway, Droll Yankees no longer makes the solid-sided plastic tube Clever Clean sunflower tubes for the CC12S (though they do make them with mesh sides now). They also no longer make or have available the proprietary trays (again, the CCT or CCT-S). That also means the plastic plug/screw that holds the tray to the feeder is also unobtainable. Has anyone needed or found a workaround? Also, you should know that the lifetime warranty applies only to squirrel damage. If I had to attribute a source to my damage, I'd say hawk strike.