Most electric pressure washers will have plastic bayonet style connections that are specific to their brand unless you purchase a prosumer/professional grade machine. Kranzle makes one of the best pressure washers in the market, their pumps are extremely durable. I would actually recommend purchasing a Kranzle model K1600 or this K2017. These models are going to be top of the line products in this category. Another couple modesl I would recommend that are more in your price range, would be Campbell Hausfeld model CP5101 or AR model AR620. Both models are great quality machines.
As for the foamer attachment, if you purchased the CP5101 or the Kranzle models, you could purchase the MTM Hydro foamer model 14.0263. Unfortunately we do not carry just the foamer attachment for AR pressure washers, you would have to purchase AR's spray kit. I am posting links below to both foamer products:
AR Spray Kit
MTM Hydro Foamer