The screw you are looking for is a brass oval head 10 x 28. My two local hardware stores do not carry this size. So I purchased a 10 x 28 tap and die and use a 10 x 24 screw and make my own. So far that all seem to be working and holding.
It is not originally a 28 pitch, it is a 30 pitch, a thread that has not been used in years…. Trust me, My Toolmakers bible says it has been too many years but that is the original thread size…30… not 28.. I have confirmed with my thread pitch gages….twice…you can rethread it to 28, but then the next guy that tries to replace them will screw it up even worse…