Need help identifying this drywall anchor used to lock in a ceiling air diffuser
I have installed quite a few registers like that but have never found them for sale. I have made them out of scraps of polypropylene, and UHMW. Most had to be shaped on 1 side a belt sander worked well for that holding the plastic with pliers. A few I could put in without shaping but not very many.  Note if you drill the hole with a drill it needs to be smaller than the screw size the screw needs to bite into the plastic and rotate out when tightened.