I am sure you know, but all creedmores chamber with the same gauge. 308 also with 243, 260, etc.
They were available recently in several sites online. About $30 per each go and no go. Brownells, Grainger and Midway from just a quick search.
Put a single layer of adhesive tape (plain old desk top dispenser tape) over the go gauge and it become a no-go.