My answer just recently today from motion pro is 4mm x .7, readily available for shipment
now that I have a clue, I will dig out my metric tap set and verify before ordering, all over the USA for 15-20$ shipped to the door, multiple vendors.
Thanks. I have a new 5mm set laying around for years, maybe I'll just drill & tap for 5mm if there is enough material. A little stronger than the 4mm parts too.
I am waiting for the return answer to that question, they first answered only they were 4mm x .7, I went to order some, found two versions with no specification difference i can find. I will post the response as soon as i get it.