I, too, have been refused travel insurance so know how you feel.
Someone has given a link to travel brokers and this is the way to go but do start saving. The policies will be available but at a cost. Once, my insurance was more than the holiday.
Please do not consider travelling to the States without full travel insurance. Even a minor trip or fall could cost you thousands. I hear of horrific costs - £100,000 would not be unheard of for a moderate procedure/operation.
Oh, it may be worth considering a one-off policy, not an annual, as these would probably suit your need and thus you'd save overall. Unfortunately, travel to the USA and/or cruises is the most costly of all.
I am sure that your husband would love to see his son so blow the money - just go!