Unfortunately, cassette toilets and portable toilets are often viewed as cassettes but they are not. The primary difference is that cassette toilets are permanently mounted with water tank, bowl and for some venting are stationary and only waste tank is removable. Cassettes often have wheels. Portable toilets have upper flush water tank with bowl connected to the lower waste water tank. This complicates the search for camper vans with real cassettes.
Here is an example of misinformation, all toilets are portable but are called cassettes.
https://www.bestreviews.guide/casset...E&gclsrc=aw.ds
This is good discussion about portable and cassettes.
https://blog.campingworld.com/gear-a...right-for-you/
Regarding OP question, I have never seen a list of campervans with cassettes. A potential search would be to contact Thetford (C220, C402) or Dometic (STS4110) and ask them which manufacturer in US uses their cassettes. I think these two companies are the only one making actual cassettes toilets available in US, but I could be wrong.
Going off on a tangent, we have Thetford C402 cassette toilet since 2013, we use the camper van primarily for a few days’ long trips, for us cassette is great. I would be lying if I say the I love carrying a heaving tank and dumping it.
If we would use our camper for longer trips, weeks/month long, we would most likely have a marine style double macerator waste system (Like Davydd) which could be the easiest one to keep it clean and have no odor, there is never a direct access to waste tank for the living space. The firsts macerator liquifies waste solids so there is little chance for solids to stick to black tank walls hence keep it clean.