We got a cover from Cover Giant made specifically for the 16-17' Casita
. They had two - one for sun and one for rain. I amin objective was too protect the finish from sap and needles from the fir trees. Cost was less that $200 delivered.
The quality seems good but we do have some damage in less than a year. Part of is was from an ice dan that formed behind the gutter last winter. Duct tape will extend the life for a few years.
I do not know whether they have one for the Bigfoot
or if the Casita
one would work (it is norrower) but at least that gives you a place to start.