Mike,
The only insurance I have experience with is through RV Nuccio and Assoc. I carry the policy through them with the ADJA. I am not a card carrying member of the ADJA, but they have an "insurance only" membership that gets you their group rate with RVNA.
ADJA annual memb is (was at the time) $99. Liability with RVNA was about $175.
No minimum revenue/receipts, etc. No requirements at ALL really.
This may be because their policy isn't the best, I don't know. I admit I didint run it up against a host of other choices before signing up with it, but it serves the purpose, and even never having to call on it or use it, the number of gigs I get per-annum just with the certificate of coverage alone over guys who dont have it makes the yearly outlay worth it.