I'm not familliar with the innards of the lite-boy but I have a small 3.5lpm, 12ltr sprayer that I use for small jobs and it looks simillar inside except it has no controller, just an on/off switch and a fuse.
If you tend to run it flat out as I do with mine, just remove the control box and wire the motor directly to the battery via a switch and a fuse in the positve wire.