If you look at the Mitsus made in the 90s most all of them have serpentine belts. I would grab one from a V6 pickup or Montero as my first choice. Try to get one from a truck so it matches the flow specs of the steering box.
Mitsubishi uses PS pumps that have a liner flow output, the American pumps are variable flow, more rpm more fluid. As others have found, they do not work.

Cheers, Charlie
If It ain't broke, Modify it!
87 Montero turbo Converted back in Spring1989
95 Montero SR 3.8 DOHC Only one?
93 Pajero 3 door 6G75 Mivec with paddle shifted 5 speed
Then a Gen2 SR with full coil independent suspension.