I did some serious looking into that, and ended up buying a 4-pan Cambro clone from Rubbermaid.
What I could tell for the official Cambro products, they have the one with the handles that stick up on the front and back, that one I think uses a gasket and holds 3 pans. There's a different version that holds 4 pans, that one can be had with a regular insulated door or a heating door (electric heating, not suitable for KCBS).
Looking back, I wish I had bought a 3-pan version instead of a 4-pan. It's just plain overkill, I don't need to hold that much meat at once, and wasted space means your meats don't hold temp as long. Ideally you want to load that sucker up for things to stay nice and toasty warm--the more thermal mass, the better.