If it is a 3-48, Brownells does not carry it and the H/R parts list does not identify the screw size or number of threads per inch for the any of their screws and they do not list any plug screws anywhere Brownells or H/R in that size that I can find.
I do have fillister head 3-48 screws in a screw kit, that I got from Brownells years ago, but Brownells no longer carries them.
Brownells does list a tap for a 3-48 but no die in that size.
The standard screw in that diameter seems to be the 3-56, but no plug screws are available in that size.