It's unlikely that any remaining warranty will be transferrable, but who knows? At any rate, you can get the "Parkland Plastic Kits" directly from Heartland Customer Service. They run something like $40 each, after shipping. 10% less if you're a HOC member. Figure one kit for each slide. The kits contain two long (48" I think) pieces of the plastic with PSA tape on them, along with a tube of the 105 Sealant/Adhesive. They do not include the aluminum edge trim, however. That you have to order separately or fabricate from roof edge molding or have it bent to your specs (I did) at an aluminum siding dealer. The cost for that can range from $9 to maybe $15, depending on what you use and where you get it.
If you look at some of the other posts about doing this modification, you can see that it's a fairly simple job.