Thanks guys. Ordered a new one today, $10 apiece, but I guess it's worth it. Saw is a dead puppy without it. I guess it's just a tad longer, but the IPL for the 290 shows the threads (part #12 below) as typical (say 1.25) not coarse like the original:
And, on the 290 there is a lip for the bar's wider slot. The 192T has a narrow-slot bar. This part is on back order, of course. Owner joked that they are hard to keep in stock because "These bar studs are notorious strippers."
Also, it worries me that the reason Stihl does not show par #12 above on the 192's IPL is because Stihl offers no part like #5 with a coarse thread and no lip required for the wider bar. So, if that part is to work on a 192, I will have to machine off that lip and pray that there are enough threads for the bar nuts to hold the bar tight to the case. Otherwise, I will have to somehow add threads, and the steel used on collar screws is tough stuff. In short, guys, I am still not out of the woods.
I cannot recall ever stripping a collar screw (stud) on a chain saw, but several members here have told me that tree service companies are indeed experts at it. I have to agree.