I have a the ryobi foam cannon and electric pressure washer and it works well. The only down side is that goes on the end of the wand instead of up by the gun so it is a way out there on the ryobi setup.
Thanks for the prompt replies guys. Liked the Chem Guys one also, saw there are two types, which one would you get if buying now? Foam Cannons & Guns | Chemical Guys
Ok so I lied this is the foam cannon I got, I have used the Chemical Brothers solution but like Mean Green better. It's on Amazon for like 16 bucks....
Got this one today with mean green soap. Works great, and got a full set of nozzles and extra gun for quick changeover while pressure washer is running. When using higher pressure nozzles, need to hold on tight. Nice to spray in tight areas like wheel wells without a long lance.