I'd talk to Brad Banks, Fred Russell or Mike Klinkenborg. They are probably selling insurance about now. Either that or pharma.
gmac i ionly pay about $250 a year
Most preferred carriers will not insure converted buses. It's due to liability concerns.
Think about it. What most converted buses used for? Partying, tailgating, etc. All tend to coincide with alcohol use. Large group of people + alcohol + large vehicle = huge payout if/when something bad happens. A company is not going to risk a huge payout at a premium of $250.00 a year.
Can't remember who we use for the RV but it's under $100 a year to cover a 1977 class C that we just put liability on. We only paid $2000 several years ago. Surprised you are having a hard time finding even just some basical liability coverage because nearly any insurance company should be able to do that.