Thanks to those who have referred me to etrailer.com, dust caps were my second purchase from them.
Again, that lack of standards thing raises its ugly head. The etrailer.com site lists the dust caps by decimal sizes (i.e., 1.954"). The local auto supply has a few sizes in stock, all measured in fractions (i.e., 1-31/32")
Why can't manufacturers and distributors stick to one scheme? I had to get my phone/calculator out to learn that the 1-31/32 was too big (1.968") and the 1-25/32" (1.781") was too small.
I doubt anyone is able to measure the inside diameter of the hub with a ruler marked in 1/32" increments, so most people could be reasonably expected to use a digital caliper......
I ordered 1.943, figuring that seven thousandths under my measured 1.950 should produce a snug, but not forced fit. We'll see when they arrive.
Thanks again to whoever pointed me to etrailer.com