I just looked, the spacers a simple piece of pipe 28mm long
it fits over the treaded end of the bolt a bit over 15.5mm.
the OD is about 26mm
If you have a mate with a lathe get him to chew you one out of a length of 1" aluminuim rod
Actually the diameter's not critical 1-1/4 would be ok too but the ends should be square,