Where are you located?
I’m in the Midwest US and options I found were CBiZ and Proper. I went with Proper.
I have been told that Travelers and Farmers and Foremost and StateFarm will cover but they couldn’t run fast enough when I uttered the phrase Short Term Rental. Even in the area I’m in, which is a very popular tourist area, I struck out until I contacted Proper and CBiZ.
Have you tried contacting another local BnB in your neighborhood and asked them who covers them? Probably a long shot but might not hurt to ask …
Good luck!