there are a couple of guys here in NY that have them on a variety of bikes. I believe the metal covers are originally made by beet and that yaimya took the design and replaced the beet logo with a 750 four logo. Anyway I am pretty sure they are no longer available from beet. However they look really really nice and add something different to the bike. If the yaimya stuff is the same quality as the BEET stuff then I imagine they are worth it.
FYI if there is stuff in japan you want yahoo auctions is a pretty active place for motorcycle parts in japan. There are several companies in japan that will help you get the part here too. The cb1100f.net website has a good writeup on this and if I find the link I will post it.
Some the japanese stuff amazes me. Those japanese guys here in the city always have the coolest stuff. Right now the new thing they added was clear plexi engine sidecovers. I have no idea where they got them but they got them for kz1000s and a cb750.
although not a cb, here are a few images of their bikes: