Hi Justin … and welcome
First of all I should mention that the “air bladder” mattresses IMO offer very poor value and should be avoided. They are not a good choice for a support layer as other materials are available that “naturally adjust” to different sleeping positions far more effectively than air. For an “in depth” look at airbeds or air bladder type mattresses … there is an article here which goes into some detail. At best they may be OK for some people who only sleep in one position but even then I believe they are not a good choice compared to many other options.
There are many manufacturers who are offering side to side split constructions in their mattresses and these are especially common in some of the better online factory direct manufacturers such as some of the members here. Even most local manufacturers who have an actual factory would be able to do this and have been doing it for years. Some of the mattresses available in chain stores and other outlets are just starting to do this now but at outrageous prices. The Kingsdown MySide series 6 is among these. It has an unbelievably horrible 8" of polyfoam and a meaningless 1/2" layer of memory foam above the coils … and I’m amazed they have the nerve to sell an entire mattress worth of polyfoam over an innerspring for this price. This mattress caters to the worst trends in the industry today and the only thing that even remotely justifies the price (even if it was 70% off the listed retail) is that it has a feature that has been available for years through independent manufacturers, many of whom can make a mattress any way you may wish.
Post #4 here was also in response to someone who was looking at the Kingsdown Series 6 in Philadelphia and has some information and local outlets that should be helpful.
Phoenix