VWbuild,
Deathbysnusnu is correct. These are custom fabricated plates. You don't necessarily have to have access to a machine shop to fabricate parts, but it sure helps!!!! I lucked out on my fork design and a lot of it lined up perfectly (Rather be lucky than good). In my case, the Harley rotors center to center were 10mm narrower than the CBR900RR caliper spacing. I had an old Kawasaki rotor that was 5mm thick so all I had to do was lay out a plates with 2 holes to line up with the caliper bosses on the downtubes and 2 holes to line up with the caliper mounting holes when the caliper was in the correct position on the rotor. Haven't been down the road with this combination but if it doesn't run out well, I can always get the Harley rotors and build a new set of plates to fit them to the Honda downtubes.
I built the Honda/Harley axle and rotor plates using a $60.00 Harbor Freight drill press, a $50.00 Harbor Freight belt/disk sander, a Sawzall, and various hand type implements of destruction. Not quite Burt Monroe, but close.
Another option is to check out All Balls Racing
http://www.allballsracing.com/ for their fork conversion kits. They have a list of bearing kits for putting just about any fork on any frame. The only thing that you would have to check is the top to bottom triple tree dimensions. You might have to fabricate a spacer to get the triple tree spacing correct. You might even come across a good used Harley or custom springer on Ebay or CL that will fix your trail problems.
To me, the research and fabrication techniques learned and problems solved is the fun part (not always when I'm in the midst of a problem). I'm nowhere near Deathbysnusnu's level of competence but I'll get there someday.
Remember, Google is your friend. I have spent a lot of hours and taken a lot of notes and sidestepped a lot of problems with Google.