Just saw an ad for a new company.
https://www.cyanwireless.com/
They provide a router that uses a cell tower. Unlimited data (well, up to 900 gigs / month), no throttling, no contract, flat rate ($109/month) and it's "portable". [They also have a router specifically for RV's.]
I have no experience with these folks, but what I read sounds pretty good and since there's no up-front fees or contract...