Sorry, but I can't help there; I need half a dozen myself!
That's the BAD news. The GOOD news is that there are NO problems in having them made. There are no tricks to Ross Rifle screws; thread form on all of them is to US standards.
Any small shop lathe can duplicate them for you. PITCH (TPI) can be determined quickly with a $5 gauge from Harbour Freight.
Hopefully, someone here who has one on their bench might post the OAL, shank diameter and Pitch.
Best of luck!
