I haven't pumped aircrete but I know a lot of companies do. Any pump designed to pump mortar, or concrete would work. There are piston pumps, screw pumps, peristaltic pumps. A trash pump may work also.
I'm sure you can make a foam generator out of a cheap water pump, I just don't recommend any specific pump. There are too many choices and non of them are as good as the Aquatec pump model PDP5853, 1.5 gpm @ 90 psi. Aquatec makes it special to our specifications. The plans you purchase provide the information you need to understand how it works. If you are so inclined and knowedgable you can modifiy the design to work with other pumps. If you dont' feel qualified to do that, I suggest you simply buy one of our Aquatec pumps. They are the best quality pump I know of and have a 1 year replacement guarantee.