Where to Buy (Very) Narrow Brighton Sash Fasteners?

I've bought and tested a few narrow Brighton sash fasteners for my new double glazed sash windows, yet none of them are narrow enough, despite them being the narrow variety for the modern sash window.

The screw arm of the back plate (body) never has enough clearance. The back plate needs to be 10-11 mm wide (most are 13-15mm) or the screw arm needs to raise or spring back quite far - even further than what most manufacturers offer.

Has anyone had this issue and have been able to find a stockist that provides these narrowest of fasteners? The alternative is to just go with the standard Fitch fastener, but much prefer the traditional look of the Brighton.

Many thanks