thanks previous respondents.

i briefly looked into "umbrella personal insurance" which is said to cover gaps and overages not covered by auto insurance, but many of the places require you to have tenant's insurance before you're allowed to get umbrella personal insurance.

next, and more promising, i contacted a local traveler's (brand) insurance agent, and after explaining i might be interested in switching to them if they could provide some kind of "written" understanding, for more peace of mind, they said what may be the magic word, an "endorsement" a.k.a. "rider" could be added. we'll see!