Replacing trim/screw cover around door & bunk ends

The vinyl trim that covers the screws around the door and bunk ends on my HTT is dirty, moldy and drying out. I'm looking to replace but not sure what size or how to measure. This is a link of what I think I need...but not sure if it's 1/2", 3/4", 7/8" or 1" Any tips on how to measure? Is is better to get some that is a little too wide?

Vinyl 7/8" Marine trim