Maybe instead of biking cross country, you can buy a used Jeep Cherokee or Mazda Miata or something with a removable roof, fit it with a bike rack, and occasionally bike in certain areas?
So long as you don’t do any damage to the vehicle you can probably sell it for what you paid for it- cheaper than a rental!
[edit] a better vehicle would be a Plymouth Sport Fury or Pontiac Catalina- you can carry more stuff and you’ve got two beds with room for people under 5’10”. Nobody would road rage against one of those cars driving sight-seeingly slow.