Hi Andy,
I know there are braces for the K2. At least here in Europe. If you wamt can look into that.
Cheers, Rob
A brace for the K2 does exist, or has existed. BGFootball had one from Telefix that was special ordered from telefix Europe. I tried to get one using the same source and they told me no more. His bike does not have a front fender. I can't tell but from the pictures I don't think it will allow the stock fender.
The problem with CB750-K2 is that the top of the fork leg is lower than the top of the tire. It is the only motorcycle in the entire world like this. The telefix brace has a really high arching bridge to clear the tire, can be seen on BGFootballs Cafe Racer bike if you search for his pictures.
So NO brace marked as K3 or later will work as they are straight across bridges type braces. After K3, the fork leg was higher than the tire, and a traditional bridge type brace could then be used.
There have been some other braces made as a loop to the front and rear, but they interfere with fenders and dual discs. Since the application is just for CB750 thru K2 its not a high priority item.
It is not a simple issue. For example, none of those listed in TurboGuzzi's link will work.
I have a "tweak bar" style fork brace which the origianal poster doesn't want. I will also be having a machine shop make me a telefix high arch style, but with an 18" tire, so not as high as for the 19"tire. It will also have a different fender mount built in.