Guy,
The module was available as an option for those who were able to receive stereo signals (and could afford it).
I don't think I have any spare modules and be prepared to pay a nice little sum if you find one.
Not surprisingly, the owners don't want to part with them.
Note that there are two basic types of MPX modules.
There are exceptions but generally one will fit both
the Beomaster 900 (Master 610) and Beomaster 1000,
the other will fit the Beomaster 1000 but will only work in some Beomaster 900's.
Mounting is fairly easy.
Two large solder points, three screws, one holding a transistor on a heatsink,
one plug out and another in and,
depending on the version of Master 610, also a socket and a lamp is needed (check if the stereo lamp is on when playing tape/phono).
Martin