Drew,
Other that HD having the small rolls of Ditra nobody stocks it on Maui that I am aware of. But a lot of people on Oahu do and will ship it if you want some. Dal-Tile, Sunset, and Central Tile Mart. Ceramic Tile Plus here has the kerdi board tub deck on display but haven't decided to stock it yet.
In fact the Schluter rep stopped my my 'massive' 100 sqft shower project yesterday in Honokowai. He was there with Bob the owner of Sunset Tile from Oahu checking out some some slip/trip stuff at the Marriott. (But I was installing a Hydroban shower, oops)
I think the Kerdi is a great system, I just prefer installing Hydroban. And it is stocked on Maui.
And to get the thread back on subject this is the little shower I am working on. Porcelain walls, made my own travertine shelf.
This is the job that the plumber's guy hit a bunch of electrical, telephone, and cable lines when trying to fix a corroded cast iron drain line below the slab.
Finally putting the shower back.
Drew - you work by yourself or for someone else?
And by the way Hawaii beat the favored Texas team 10-0!
Like they say, "Don't mess with the Aloha State"
Just wish the Sugar Bowl against Georgia worked out the same way a few years back.