Thus far Manchester Tank is the only source I've found and they're very proud of a 110 gallon tank - to the tune of $1600. And a 48-gallon tank is not much less expensive ~$1300. Both seems pricey to me, but what do I know? Meanwhile, I've poked around on eBay but only found 30 pound horizontal tanks (meant for lift trucks).
FWIW, a gallon is about 4.2 pounds, so a typical grill bottle, e.g one taking about 20 pounds of propane is about equal to 5 gallons of gasoline. Moreover, fuel consumption between gasoline and propane seems to be close enough to call it the same (90% actually, which is close enough for government work in my view). Thus, the 6.5KW Honda we have available to convert to propane is still going to go through roughly 12-15 gallons per day, e.g. whether it's propane or gasoline.
Of course, the principal reason for desiring propane is the lack of a shelf life for the fuel. Anyway, I'm open to thoughts for a less pricey solution for a propane tank (I'm in central Florida).
Reference data:
Manchester:
http://www.mantank.com/pdf/Propane%2...20Vehicles.pdf
Calculating propane use:
Propane and propane generators