You are some kind of detective and that parts guy IS some kind of savy....
I guess I will not bother trying the bolt houses here in Austin... very small town attitude towards keeping stuff in stock.. and I never run across any savy counter people....
I would appreciate you putting a ruler next to the threads and telling me how many threads there are to an inch..... It looks like I may have to use my lathe to make mine.... Thanks and bravo on your work.