Leslies has CYA reagent (I think it is Taylor R0013). As far as I can tell, the CYA test is 1/2 water, 1/2 reagent. The actual amount of each probably?? doesn't matter that much, but you need enough to be able to at least partially fill your sight tube.

You have to ask for it at Leslies, it was in a different place than the other reagents for some reason. (Oops, waterbear must have posted just before me).