Have you tried the specialist Classic Car insurers or brokers ? Gott and Wynn, Towergate, RH Specialist Insurance, Carole Nash, Footman James and Heritage are brokers who regularly advertise in classics magazines and there are lots more. Your proposed car might not be old enough but you could at least give a few a try. I've had experience of Towergate, Footman James and Gott and Wynn and managed to get reasonable prices from all of them along with agreed values but most of our cars are older than yours.
Buy yourself a cheap classics magazine and have a look at the adverts and think about having a look to see if there is a Honda club as you will usually get a discount with membership of a relevant club.