I previously had tire and rim insurance for my C7 but it lapsed, and the issuer is no longer around to re-up.

Is there a preferred dealer around that provides fair rates?

Apologies if this has been asked/answered, but I searched the C7 forum for Tire insurance and didn't find anything.

 

I've never heard of it. However that should be covered by the comprehensive insurance in your normal policy.
Check with your agent...