my dad recently travelled to USA and stayed for a week then travelled back on Queen Mary 2 and he got insurance either with insureandgo or staysure, can’t remember which. Dad is 74 and mum 72, dad was diagnosed in April 2014 and now good partial remission but not able to have stem cell transplant. The total cost was about £350, I think which isn’t bad for USA. Other myeloma sufferers have suggested:
World First
Insurancewith
Hope this helps