Give them a call, they may do it cheaper, they are very close to galveston yacht service, on harborside drive aka port industrial blvd.
If they cannot do it I saw this and it may be an option they advertise it as a "trailerable" water proof boat cover, and an alternative to shrink wrap. I would think the guys at Galveston Yacht Service would be able to secure this type of cover with minimal effort or expense.
It shows the cover to cost $80.00. Thats the first site to come up on my search Im sure there may even be cheaper or better ones than that.