Front calipers

Hi, I'm new on here so my apologies if this has been covered before.
Does anyone know if any other calipers fit standard fork mounts on the 13? Or if any fit with minor mods. I have a 1981 UK reg z1300.
Thank you everyone.

There is nothing else that will fit straight on.

Some people have made caliper adapters but not seen any for a long time.  Pretech in the UK used to make custom 6 piston calipers that bolt straight on but they aren't operating anymore 

The German shop does a 320mm Brembo 4 piston front brake conversion. 1400 Euro