John, the word "spastic" is a technical term for the type of increased muscle tone seen in some forms of cerebral palsy. It's still used to describe those forms of cerebral palsy, i.e., "spastic diplegia" or "spastic hemiparesis." You're correct that there are organizations such as "Spastics International" which use this term. However, I would be very surprised if there were an organization that used the word "spaz" (or "spazz", as this manufacturer calls it).

Aloha,
Mark