Hi MiscellaneousBeef,
Welcome to the Mattress Forum! 
Some of the better sources of which I am aware for latex componentry are listed in the component thread here. Many of these suppliers can create custom sizes for you. Most of the latex you’re likely to encounter will have pinhole construction, not only to change the comfort of the foam, but also as a by product of making the curing process consistent. The extra breathability this affords is a nice extra bonus. In North America the longest “standard size” mattress is the California King at 84", but the widest “standard size” mattress is the traditional king at 76". But layers can be seamed to create virtually any size you desire. Latex cores tend to top off at 6" in thickness, so you’d need at least two layers to achieve your 8"-9" overall thickness.
As for the buckling column gel, here are three manufacturers that have different versions of buckling column gel. One is Intelligel and one is NexGel (now owned by Spring Air / Sommex since Natura went bankrupt) and Leggett & Platt now has a version called Somnigel which is being used by King Koil and several other manufacturers in their mattresses.
A forum search on “orthogel” which is used in the Nexgel mattress or on “intelligel” used in the Intellibed, or on “somnigel” which is a newer version that is used by several manufacturers (you can just click the links) will bring up more forum comments about them.
I’m not aware of sources to the public for custom sized buckling column gel layers, so this may require you to do some phoning directly to Intellibed or Leggett and Platt with your request to see if they are able to offer you any advice/assistance.
Phoenix