Kithas had four strange dust for 7 silver 20. I just purchased all four and now she has none. ,,,, You just have to wait.
Not sure if you are fimiliar with the way it works but some in the game must station their alts at vendors. I mean sometimes takes me weeks to get the Runecoth Bag pattern from Everlook. .. for eg.
Really though pretty much any low level green will give you strange dust. Haven't you got a character with tailoring to make some greens so you can disenchant them. Just made two red linen robes and got strange dust each time. I mean that is how you generally level these profs. Tailor/Enchanting