I had all the gaskets replaced on mine a couple of months ago at Redlands Truck and RV (Calif and I see you are from Texas). You could call and talk to Chris about where they were able to get mine. I know that one of them took three different vendors to locate the correct ones. They did not have to remove the slide. As you would expect, it is not a cheap job.
2001 34' Alpine Coach
2008 Jeep Rubicon or 2012 Ford F150 4x4 Lariat towds
or a couple of different trailers
Retired in Apple Valley, California