I have one... I got it for $24.75 I think. I know where you can get one and I could PM you if you'd like... If they don't have any left right now, they might have more in early Spring.
I've kept robcantleyi before and seen them even in flawless conditions, and they seem EXTREMELY fussy... Like more fussy than any other Nepenthes. They're probably more fit for the terrarium environment, as mine hated my winter temperatures. Ventricosa x rob, on the other hand, is much easier. Mine often dries out and keeps on growing and producing nice pitchers. It's also right by the door of the greenhouse, so temperature and humidity swings much more from day to night and season to season. It grows quite fast, as well.
Contrary to what Paul said, I kinda enjoy mine. It isn't my favorite, but it my be a personal opinion thing. I like it because it has the ventricosa shape with bigger pitchers and a more fleshy peristome. However, you'll only get that when the plant is mature, which will take a while.
It's definitely not a hybrid to stress over, though. There are much nicer hybrids. This one will likely only look nice when producing upper pitchers, and I think there are many different clones of the hybrid... So even if you do find one online, you may end up with an ugly one.