EBR black anodized quick release (non lockable) fuel cap. A popular upgrade for XB / 1125 bikes. New - never installed. $185 shipped in the US.
There is a tiny little nick (see red arrow) but not really noticeable
I like the engraving. I got a silver one awhile back when I went keyless for the track bike. Do you have problems with overflow out of the hole in the frame full tank/aggressive riding? I got mine fixed, but just curious.
Problem #1 was the gasket didn't seal. Permatex #2 (non-hardening, and the only gas submerged rated sealant I know of) solved that, then that tiny barb was too long and just creased the breather hose when I installed the cap. I unscrewed the barb and drilled the threaded hole slightly smaller than 5/32", then stuck the hose it comes with right in the hole (I even had to notch the mounting boss for the top left allen for that tiny hose to pass without creasing), out the drain hole on the left of the neck, under the airbox, down to the bottom.
A PITA, but it solved the issue completely. It lets fumes out but is too small and too long for any significant fluid flow.
Sorry for the novel and hi-jack, but it seems they all have this issue.