It seems that there are universal split boots that should fit the 123.

In UK seems they call boots gaiters!

This is a universal model.
This boot is suitable for shafts 19-35mm and CV joints 56-110mm. Our cars are in that range, I believe (25 & 64mm ?) There may be others. For example, Stickyboots.

__________________
Graham
85 300D,72 350SL, 98 E320, Outback 2.5