as far as I remember it is the same coupling on the Maramu (Vetus Flexcoupling model 6 35mm shaft (KO53)).
In case that's true I just wanted to let you know we have the coupling here as a spare - bought it last autumn to replace when we next time get on the hard. That did not happen so far, will only next winter and until then we are going to travel to the states and canada and can buy replacement. We don't have any bolts though... Let us know if you need.
Jochen and Traudl
Maramu #143 Blue Song