They have a complete line of tool steel, stainless steel and other ring materials available with a wide variety of coatings on them. They have rings in virtually any size you can imagine. I forgot how clunky and junky their website is. I can’t find the ring set I run on that thing either, and I don’t run a ductile iron moly top ring. I believe I have an AP stainless top ring and I can’t think of the coating on it, with a Napier second and a standard oil ring because of the HV pump. So you may have to call them to get the options. Or email Lake Speed. That’s what I did. I forgot to mention if you tell them your machine shop is measuring surface finish with a profilometer I’d bet 5 bucks they won’t sell you a moly ring.