The lower fork mount that you can use is from Memphis Shades. It's for a Kawasaki VN900, and also fits Honda VTX 1300, 1800, Suzuki C50, and Intruder. Part number M9898. Old part number is 2321-0038. I will be getting these myself. These are just the brackets. You have to make your own lowers. These will work with the 07's for sure, but should work with the newer bikes too. I can measure my forks with a caliper if that helps.
CLICKY Shutterbug has these on his '07 Speedmaster.
HTH,
H.
