I'm using an old stair wand that came with my truck when I bought it in 96 (its a used truck from 88). I think its like the basic ones from
hydramaster. about 8" wide, 2 jet, the head is almost 90 degrees to the 1 1/2"tube, about 3' long. It helps to keep my back straight when doing stairs so I'm not hunched over. I had a shield welded on the back of it to reduce the back mist.
Its nice for getting under low items without moving them. Comes in handy for the couple of restaurants that I clean that have wall mounted tables; hard to get the floor wand all the way under.
Sure beats cleaning stairs with a hand tool or worse, a floor wand.