Heres a place that sells CYA reagent.
http://www.poolweb.com/Shop-On-Line/...-Cyanuric-Acid
They have 5 different sizes.
3/4 oz = $2.20
2 oz = $3.29
16 oz = $7.67
32 oz = $11.53
Gallon size = $23.65
I bought 16oz last year. Shipping was around 10.00.

~Hoffmans