Ahaaaaaaaaa

Maybe it's easier to swap the fuse from one of your other switchers (if it's the same).
I just took a look at the wiring diagram, it seems that this is not an ordinary switcher as it has + and - sense lines which are normally used to automatically regulate +5V.
According to the schematic:
"-" (brown wire) = GND
"+" (red wire) = +5V
"+S" (red/white wire) = + sense
"-S" (brown/white wire) = - sense
(I guess other voltages are provided by the Audio/Regulator Board)
So I'm afraid you will have to use this switcher. I know how to bypass the sense lines on the older Atari Games, no clue how it works on Gauntlet though. I don't think that leaving them unconnected would work.