Relative to the centreline of the caliper (lengthwise, between the pads), is the rotor near the back (i.e. 'inboard') or is it fairly evenly centred. If it's 'inboard' (very possible given the description) then you can by a thin wheel spacer (3mm? 5mm?) and stick it behind the rotors and then use otherwise as is. Ideally you want the rotor to be fairly centred in the caliper. If it's already fairly centred, depending on the way the pad bracket/caliper mount is setup, if it mounts on outside (wheel side, not car side) of the knuckle then you could add a washer/spacer (3mm, for example) between the bracket and the knuckle and then add an equivalent spacer behind the rotor and it would shift everything out.

Hopefully that makes sense. I can try and draw some crude pictures later if not.