Call a couple of machine shops ......They should be able to make what you need at a reasonable price . You can specify the alloy or supply the material .....McMaster Carr is one source ...a little pricey but convenient .

McMaster was the first place I checked. I think I am on the phone with them weekly for this project. They have plenty of coarse-coarse studs but no coarse-fine. And 9/16" they only carry in 18-8 grade, not 316. Initially they thought they could get them, but then they no-quoted me. I have the capablility to make them myself, have lathe will travel, but with a long list of fabrication items, I am trying to make the balanced choice between time and money. Worst case I guess is I'll buy an extra long coarse-coarse threaded stud and then cut the fine thread the other side. I talked to Matt at TNT and he thought most of the Merc Studs were roll threaded verus cut.