I built my own a couple of years ago. Its a down draft design & is about 33" wide 18" deep 18" tall. I made it out of MDF & hard board & sprayed the inside with a non flammable coating that we use in our spray booth at work, its also white in color.The coating is removeable, it peels off.
It uses 2 filters ( from Lowes) & vents out a basement window that I can crank open, I kept the exhaust run short & is 6" in dia. its metal & grounded to the motor which is also grounded.
I used a 2 speed motor with an enclosed cage from Grainger. I use the slow speed for a/b small parts & the high speed for cleaning out the A/B or for using spray cans.
For lighting, I use 2 LED strips that sit in the top of the booth & are covered by a piece of glass so I can keep any over spray off the lights. There is a 5" ledge that sits in front & I use a small turntable to paint on, rather than trying to spray deep with in the booth itself.
To be honest, It would probably be as economical just to buy one.However I had all this material including the motor just sitting around from other projects., so I put it to good use . The only items I bought were the LED lights & they were not cheap, but they gang together electrically & were low profile & produce no heat & should last for 20 years or moire.
The booth just works great & I spray lacquer all the time ( I still wear a respirator) The wife never complains of any odor..which we all know is the real test :)
Hope this helps you
good luck
Steve