Hi Eagle007,
The two best places I know about for zip covers are …
https://www.sleepez.com/mattresscomponents.htm
A picture of the sleepez non quilted cover is here (except the lighting is off and it is actually off white). their picture on the site is actually not the right one and they will be changing it with some updates on their site.
There are a few other places but the covers are not the same quality and I believe it is worth having a high quality cover.
The advantage of a non quilted stretch knit cover is that it conforms to the shape of the latex better which can result in slightly better pressure relief. The advantage of having a wool quilting is that it is more breathable and wool helps to regulate temperature even though it slightly reduces the pressure relief of soft latex.
So you could choose the latex as “components” and put them in a zip cover purchased from elsewhere if Patrick is OK with that (he may need to sell it as a mattress). I would choose either quilted or unquilted depending on which one was closer to the testing prototype that worked for you at The Natural Mattress Store which looks to me like a wool quilted cover.
Phoenix