Sure. You can just substitute it for one of the lower red nozzles that you never use anyway. You may want to cut in with a tee fitting and an extra valve (so you can still use the red nozzle). Coil up the extra hose and secure with velcro. Use a hand sprayer wand.
Or...did you mean add a handsprayer? In that case, just enlarge the bottle caddy to fit a 1 quart handsprayer. In my case I moved it to the right hand side--it was reachable even when on the fly.
I'm considering wearing a battery operated back pack sprayer with a gallon or two of herbicide while riding my permagreen.....is that crazy sounding or what? I'm kinda giggling just thinking about how that might look....
DA is right.Tank drain valve is fine. You don't even need the tubing with the braid reinforcement. Plain cheap vinyl tubing is fine because the pressure regulator valve keeps everything at 10 psi or below. Just don't expect a lot of pressure. You won't be spraying any tall trees.