Sorry Mock
Thought you got it sorted.
I took a few snaps and measurements from my unbranded machine.
It's about 545mm long roughly, as I can't measure it without taking the collars off, I'd want 550 to be on the safe side.
It measures about 17mm wide
The rack is milled about 110mm down from the top
It looks to be 9mm thick, and the slot depth is 4mm.
The milling looks to be about an inch above the bottom.
I had to go out and check the length as I forgot
, and the narrower rule than the one shown
fits into the collar deeper...
I can't tell if the ends are ground as sharply as a chisel or not, so you would need to check that out.
I haven't checked what angle bevel they are ground at either.
I hope this helps
Had a quick look with no avail on the bay, found some return springs for a pint and overpriced cranks but no racks.
I could have looked more thoroughly though.
Might be easier with measurements.
Good luck
Tom