As far as I know, you can only get them with a carb. Let me guess, the needle jet was stuck and you gave the holder a little ass and it cracked at the bottom? (been there, done that, know better now to use a matching thread screw to tap it out with)
They're not available separately, the slides/diaphrams are but not the guides (I've been looking too).
Maybe Jay has some sort of super-secret source? Used?