I bought a stainless steel pump sprayer, added a schrader valve (tire fill valve), deleted the pump and changed out the hose, valve and spray head. I had about $100 into by the time I was done, but at the time we were using it routinely to spray carpet shampoo evenly.
After I was done with the cleaning business I started using it for weed control and big bug death. Works just fine and has for better than 10 years.
Sounds simple enough for a MacGuyver-dude like you! A good idea though. I need to find a solution for weed spray. Those hand pump bottles suck and the larger capacity ones never hold pressure and leak poison from the hoses. Maybe this could be a solution.