Weaver Tactical Mounts Top Cap screws

[HOSSONE]

I have a set of the highest weaver Tactical Mounts that I needed to shim another .125" to fit a 50mm scope on my 6.5 Grendel. So I machined a set with the proper offset radius, The problem is now the screws are to short to hold the top cap on. Looks like they are #8-36 0r #8-40 thread pitch but the size of the head does not match a standard #8 S.H.C.S. Does anyone know the pitch or a good source for screws .500" long? Fastenal doesn't list anything online that matches. Any help would be appreciated. Thanks