DBP,
I also use household ammonia cleaner as a bleach for cyanotypes. Just like you, I figured that - what the heck - since I don't have any "real" ammonia on hand and wouldn't know where to buy any, I just diluted some Windex and put a little bit in a tray of water. Works wonders. Other alkalines work just as well, since bleaching cyanotypes is basically immersion in alkaline solutions. While activity is correlated with Ph, temperature, agitation, dilution, and that sort of thing, it boils down to bleaching the print to some visually acceptable level.

Very dilute developer (paper or film developer) works. Baking soda too. TSP the laundry additive is another. I've tried a number of household items, and you probably can come across other things as well. I work with these in a rather imprecise way, sprinkling this and that by guesswork. After all, I can watch the bleaching process closely and then pull the print at the approximate time. My wife, needless to say, frowns on all my experiments, since I use up all her kitchen stuff.