The MiniPAC comes with a USB cable. If you plan to connect it to a USB port on your PC, you don't need the PS/2 adaptor.
The Ultimarc buttons/joysticks require 4.8mm connectors, except the Goldleaf buttons (the ones without an external switch) which require 2.8mm connectors. So you have to check your switches before ordering.
If i am not mistaken the Sanwa JLF requires a special 5-pin connector to connect it to MiniPAC (up, down, left, right, Ground)
You can make your own harness to your own specifications. All you need is Crimp Connectors (4.8mm or 2.8mm) and a few thin multicolor cables.