I have a simple 25 gallon Enduraplas tank. They make a 55 gallon tank also.
It is a simple transfer tank with a nozzle that you manually fill your tank with. I use a 12 volt jump box to power the built in pump.
It does the trick no installation required. I can move to my next truck or put it in another truck in minutes.
Not quite as convenient as a piped in tank but just as useful. Easily removable if you want the space back.
Works great. Use it when you want . Remove it if you want.
Very versatile and flexible
Enduraplas Tank