I'll be driving the brand new track, Thunderbolt in Millville, NJ this coming weekend, 22-24 Aug. I bought the insurance through locktonaffinity based on the recommendation of an insurance broker who's also a club instructor (actually a husband/wife team of instructors). I'm not an insurance expert but their recommendation and the fact they use the same service for their cars sold me.
It's a 3 day event, I valued the car at $61,000 and my cost was $335. There's a 5% deductible. But I'm only looking for coverage for catastrophic loss to be honest. I did the whole thing online, it was very very easy to do.
Side note: My regular insurance policy just changed in June of this year to not cover driving schools. Before that the exclusion was for competition or practice for competition. Bummer on the timing.