Went to Home Depot, Rona, Cdn Tire, 2 Marine stores, 3 bike shops (including my BMW dealer), Brafasco, and Fastenal. Talked to two friends in BC and one in Florida - for a stainless steel socket head cap screw, M8-1.25 x 70 or 75 mm. No luck!
Then, I went to the Fastenal web site. I had visited the store and saw nothing in the bins. Did not talk to the clerk. EBay had some for $6 + $17 shipping - and wait 10 days too! But, by phoning the local store and giving them a SKU from the web site, I got a special order. Will get them next Monday. One 70mm and one 75mm.
This bolt will go through a RAM B-367U ball, the left bar casting, the 20mm Touratech bar riser, and into the triple tree. The ball allows mounting of my Zumo 550 GPS.