You can purchase Eternabond tape in 12 inch wide rolls
here. Might be kind of pricy for what you want though. They also sell 6 inch wide rolls much cheaper. I have purchased 4 in rolls from them but that might be a bit too small and the overlap would not fall in the right place.
I think I would use 6 inch to make a temporary fix until you can get to a fiberglass repair place. I am assuming the hole is in the fiberglass part of the rv and not the roof.
Barney
2004 Sunnybrook Titan 30FKS TT
Hensley "Arrow" 1400# hitch (Sold)
Not towing now.
Former tow vehicles were 2016 Ram 2500 CTD, 2002 Ford F250, 7.3 PSD, 1997 Ram 2500 5.9 gas engine