I need to get one for doing my fox forks. Standard one with chamfered openings might slip off and cause issues. Any idea where, or does anyone have access to a suitable flat grinder if I bought a chamfered one and sent it to them?

mojo sell them.

EBay a 26mm box spanner.

But that won’t go on a torque wrench.

26mm is an unusual size, I’ve never heard of it being used anywhere else and I’ve worked on all sorts of odd vehicles.
My suspicion is that, as Fox are American, it’s actually 1″ AF (25.4mm). Can anyone confirm this ?
A single hex, not 12 point, socket would be best. Grinding the chamfer off would help if it’s a shallow nut.
If you’re near Kidderminster, I can do it.

http://www.mojostore.co.uk/acatalog/Tools-1.html

Get socket and file it flat by hand or take it to an engineering place and ask them to grind it flatffor you.

Loco Tuning of course.
http://locotuning.co.uk/tools.html

A little cheaper than mojo. :0)