I wouldn't be surprised to find that 9" is a typo. The guy in the video didn't say anything about them being larger.
Also, when they show the Phantom running, there looks to be an awful lot of clearance between the props.
As for props being made anywhere but China, not very likely. DSLR Pros, and everyone else import the same thing, and mark
Myself, and several others here have ordered the ones from eBay, and the fit and finish are really nice. Mine fit perfectly
on the motor shafts without any binding, or play.
The link that Gizmo3000 gave is good, and the props are already keyed to fit the Phantom. (and probably what you would get from DSLR Pros).
A set of props should not cost as much as 2 replacement motors. I would just order 3 complete sets from eBay, so as to
have replacements available.