I have an annual travel policy to defray some of the costs if I get stuck somewhere or my bag goes missing. It isn't one that covers everything on the trip. I have a Nationwide policy that cost me like $80/year. If I was looking for insurance for a single big trip like WDW, I'd look at Allianz to start.
What do you want it to cover? Plane tickets, hotel rooms, baggage, theme park tickets? Those are all going to make a difference in price and availability. Excess medical coverage.