[Amps] Spring Channel Nuts

[Roger Parsons]

Please forgive me if this is the wrong forum. 

I have been happily building an amplifier and other things into an old 19" BC transmitter cabinet. The cabinet is quite old but in good condition. Unfortunately, it did not come with the rear door, and I am not very happy about having lethal voltages around with no protection. So I thought - easy - I will fit panels to the rear which will be useful for connectors anyway.
The cabinet has fixing channels in it which are basically unistrut, and there are horizonal ones at top and bottom which take standard (spring) channel nuts. So that bit really is easy. There are also vertical channels at the back which is where I want to fix my panels and these are much smaller. To use those I need channel nuts which are approximately 10.5mm across the flats. I know that these (did?) exist as I have the three that were used for the original door. But I need more and as far as I can see, they make hens with teeth seem pretty common.
Any suggestions?
73 RogerVE3ZI