No, the mount that bolts to the carbon and stainless Westfield cans is the equivalent of the tab that's welded on to the silencer in your photo.
You can see the bit I mean in the photo below, it screws straight to the end of the silencer, using the same dome head Allen bits that hold the silencers end cap on. It then sits underneath of the rubber bush, at a downward angle, which in turns sits under of a black finished steel bracket that looks very similar to what you already have.
As the mount is welded stainless, IIRC, shaped to fit the silencer, and handed left or right, I'm 80% certain they come with the silencer. But probably only Westfield can tell you for sure if that's still the case.
(Though I have to say, the one in the photo above looks fitted a little tight to the tub for my liking!)