It's generic name is Nature 2 and its absolutely available everywhere. Some spa makers like D1 give it a different name and package but that's just marketing. D1 has Zodiac (the maker) package it in a manner so it fits in their filter basket while typcially its in a tube like container that goes inside yor filter but its all the same in the end. You can get the N2 cartridges from many on-line sources.
N2 is good in conjuction with ozone to lessen the amount of sanitizer needed but regardless of what a salesman may say you WILL still need to use a little chlorine to keep the water clean/clear. I am very familiar with N2 and myself and others here can always give you more definitive info in the future after you get your spa if you still have questions.
