I had a similar problem when I bought the Goldwing. Most insurers don't want to take on the risk of a bike costing over 20k.
I sent an E mail to LV (my then insurer) and subsequently had a long talk with LV's CEO and then his underling.
Apparently this value was set many years ago and hadn't been updated since. I explained that there was then a good number of bikes over 20k, and many more approaching that value. After a couple of days they got back to me with a satisfactory proposal. ( they withdrew from the bike insurance market the next year

)