Most parts are pretty standard throughout the RV industry. With older models you may need to do some modifications, but...that's part of owning a trailer. I've had good luck finding parts for my Bigfoot
. Often I end up doing modifications to make a slightly different shape/size part fit, because it's easier than searching through the 10,000 different hatch covers on the market...
I had a 78 motorhome for a while, and even that wasn't too hard to find parts for.