Although I haven't replaced any slide seals, I have replaced some of the seals on the basement compartments. I found an exact replacement at Uni-Grip Inc:
Uni-Grip Inc.
If you click on "Catalogs" and then "RV Seal Catalog" I think you'll find everything you may need. They claim to be an OEM supplier to many of the RV manufacturers and when I purchased the basement seals nobody could beat their price. Good luck.
Lou
05 TS Envoy 38DS04