Even 3D printed in PLA they'd still be very usable. If you don't know anyone with a 3D printer try your nearest makerspace.
Also the SMA nut is 5/16" which is only 0.8% smaller than 8mm, so something like
this from Amazon would probably do if you only need one for your toolbox, if you have room to use the length of it + a handle. The slotted nut driver style is very much preferable if there isn't plenty of flat panel space all round the SMA connector.