Is Nanogen Locking Mist necessary? And where to buy Nanogen

[halpmeplease]

I am about to place an order on amazon for Nanogen and it's 24.95 plus 6 bucks for shipping.

I'm wondering if any popular retail stores carry this? Like CVS or something?

And is the locking mist necessary? Does it help, and would you recommend using that as well?


Thanks!