I bought a 25 gallon tank with a 2.5 gallon RV Pump and mounted it to a light metal frame which I had made with two 4' swing out arms making for a total 12' wide when open or 4' closed I attached hoses opn the swing arms with zip ties with spray outles about every 12 inches. I also added a 50' hose with a wand which I coil around the tank. I mount it to a 3 point fork lift with bungee cords for 15 or so years ago.
I ran a wire with fuse under the frame of my JD 770 with an on off switch on the dash and a pig tail under the frame to a rear fender with a zip tie. The tank has a pig tail I plug into the tractor line for power. When not used for the sprayer, I have another power line at the rear of the tractor so I can use an auxillary light if necessary with a magnetic base to the ROPE.
From the pump, I run a hose to a valve which has a return to the tank and a valve to either the wand or the fixed sprayer. This way, I can control the volume and pressure by the return valve which just pumps the overflow back into the tank and I can decide if it want the wan\d or the fixed sprayer.
This way, I can turn the pump on and off from the seat, and I can drive the tractor with the wand and spray along a road etc., with the fixed sprayer off, or walk around with the 50' hose or have the wand off and the fixed sprayer for field work. It takes about 5' minutes or less to remove the tank so I can use the fork lift.
It cost a little more at the JD dealer for the parts, but I avoided the Harbor Fright or Farm Supply quality issues. If the pump goes I can replace it at an RV supply. So far, it's about 15 years old and still works when I need it.