Safeguard speedo knob source: Zip Products
 

Zip Products, in Mechanicsville, VA is a Corvette repro house. That said, I was able to source a knob for my '63 Safeguard speedo from them. The rubber knob is apparently identical to (or very similar to) the trip odometer reset knob on the '63-'77 'Vette (go figure...though that's how I was able to get new armrests for my '63 from a GM dealership: the 'Vette used the same ones as my Bonneville).

Anyway, in case this may be of use to anyone else for this knob or perhaps other parts which interchange to our cars:

Zip Products
8067 Fast Lane
Mechanicsville, VA 23111-1189

800-962-9632
https://www.zip-corvette.com

Fair prices, fair shipping, quick order fulfillment.

I was able to use Corvette safeguard speedo parts on my 67.

I wish there was an interchange book like the one I have for my '56 Safari. There are a number of parts we have in common with other marques (tilt turn signal apparently crosses with a few, as the columns were common to all but Cadillac). This knob was a surprise, though, as it was actually for the trip reset in the 'Vette, but looked exactly as I recalled the Safeguard knob (like a tire stem cap, with shoulders).