I thought about the heat with a hairdryer method, but figured that as soon as it cooled off, it would shrink again.
So for now, I cut the vinyl and reinserted into the track. It left about an inch and a half gap.
Went online and searched for a replacement. Found several sites that sell it in rolls of 25 and 100 feet. They include Walmart.com, etrailer.com and amazon.com.
I ordered from amazon.com
https://www.amazon.com/Camco-Vinyl-I...0006JLW5C?th=1