try contacting some rotor manufactures, they might have stuff like this. We just got a pulley spacer from American Wire Wheel, but I checked and they don't offer rotor spacers. (the pulley spacer is for a 2000-newer VRod only, I think). But maybe Brembo or some one offers something like this.
I was wrong it is only good on the 99-84 wheel fitments but it is 1 inch think for 79 bucks plus shipping. Their part number is MXC-1502, Drag's number is 18748, but that doesn't look right not me now. But that is what the paper says. So if you wanted to cut that one down.