KZ1000A2 1978 Rear Brake Rotor Police 18" Rim

Hi everyone,

I've searched high and low for an answer to my question, but so far no luck. I recently bought a 1978 KZ1000A2 that had been partly turned into a KZ1000Ltd. I'm in the process of reversing some of this and am looking to replace the rear 16" wheel with an 18", I decided to stay with alloy rims. I have a 1988 Police 2.5x18 rim which looks like it will be a straight swap from the measurements I've taken, other than the brake rotor My problem is the existing rotor would appear to be a 11 3/8" rotor and I can't find one that size to bolt to the Police Rim. I have a 10.25" rotor with the seven bolt pattern that fits the wheel, but obviously not the brake caliper on the bike. Is there an 11 3/8 rotor that has the 7 bolt patter of the police rim? if not what sizes are available that I could adapt to with a caliper from a different model. How big is the rear rotor on a 1988 KZ1000p? Is there a rear caliper to work with a 10 1/4" rotor?.

I'm seeing a lot of used calipers and rotors for sale, it's just hard to find them sold as a pair or to establish the diameters on various models to purchase them separately.

Thanks in advance for any help.