Seeing a few stands for this model on Ebay and even when in new condition seem to come with different screws. (55r4ax and 55r4a5r use same legs).
May want to contact one of the sellers and see if they can measure screw for you. I have come up empty with these screw specs.
Doesn't even seem to cross-reference with TCL legs. May want to just purchase a universal stand replacement screw kit for TCL from Amazon.
Will try and update if I can find exact screw for you.
Here is one Ebay link that contains stand legs and a kits of different size stand screws for TCL Roku TVS.
Ebay TCL Roku TV Stand legs with Screws
Roku Community Streaming Expert
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