Hi Urbanrancher100,
There are three versions of buckling column gel that are generally available in the market which are Intelligel, Orthogel, or Somnigel (see post #2 here). Intelligel is only used in the Intellibed and Orthogel is used in Natura/Nexgel mattresses and Somnigel is used by several manufacturers including King Koil.
Outside of Intelligel … you could contact the Nexgel site to ask if there are any retailers in your area that carry them and you could also try contacting Leggett & Platt here and ask which manufacturers are using the Somnigel and then contact the manufacturers to see if any of them have any stores in your area that carry them.
A quick google search on “Somnigel mattress” turned up several manufacturers that are using it outside of King Koil (see here and here) but a deeper search may turn up more because neither one is in California.
Some of the Natura/Nexgel mattresses are also on Amazon here.
Phoenix