Over the years I've been with:
Sureterm
RH Specialist car division
Lancaster
Aon
Hagerty
A few are being a bit more restrictive these days, but so long you meet the basic requirements you should find something cheap enough:
Usually you have to be over 25
Some require the car to be garaged over night
Usually have to be insure with regular insurance on another vehicle (your daily)
I really like Hagerty but the premium shot up last year, though I'm still going to give them a try next time.