Where could I find a return air grille that would accept a 4-5in filter?

TrueAire makes one (model 194), but unfortunately, it is back-ordered into June. Any idea where else I might be able to find one?

source https://hvac-talk.com/vbb/threads/2228593-Where-could-I-find-a-return-air-grille-that-would-accept-a-4-5in-filter?goto=newpost