There is a travel insurance sticky in the travel info forum. There is a site that allows side-by-side comparison of several carrier's plans. Much depends on what you want covered. Medical? Cancellation? Evacuation? Are pre-existing condition coverages necessary? So on and so forth.
For under 65 y.o. people who have health insurance, domestic trips paid for using prepaid TS points may be more expensive to insure than to just taking the risk yourself.
Travel coverage isn't cheap.