Welcome to the Forum! On an older trailer you might have a tough time finding something that will match. Here's the route I'd take. Take a piece of cardboard, make a template, then determine the thickness and type of material needed....Corian, formica, etc and try to get a piece of scrap from a custom kitchen factory and make my own. You can also buy a real nice piece of hard rock maple and make one from that. If done carefully it will look nicer than factory and you'll have the pride that you did it yourself. Good luck and have fun!
2010 Cedar Creek 5th Wheel 34SATS "The Beast"
2006 Ford F350 Lariat 6.0L Diesel
2003 Harley Heritage Softail "Hogzilla"
1988 Harley Softail Custom "The Fireman"
1986 Marriage to "Wifey" (patience of a saint)