I've had a random orbital sander pretty much since they existed and have never found the need to precisely centre them on the exhaust holes, although it's a cause for minor celebration when I do. Now I can celebrate every time!
This simple jig is 72mm across to fit my Bosch 125mm sander (and many others) to make it fit yours simply measure the furthest distance between holes and scale it up or down in your slicer to suit.
The author marked this model as their own original creation.