Give these guys a call (actually mostly gals, the agency is female owned), they specialize in collector car insurance and shop around for best rates for clients.
They got me a policy for my vintage cars that is around half what Hagerty was quoting when I checked their rates. Though it appears Hagerty recently bought out my insurance company's collector car business and have bought several others recently too, so I am worried they may soon completely own that market and I may be stuck with their high rates! Maybe they'll mail me their Hagerty magazine at least and save me having to pick up copies from agents who have booths at car shows...
https://www.rallyinsurance.com/