About old interface HP8750A

Hello from Spain:

Our school (Barcelona) got five old HP8750A (Storage-Normalizer). All of them have the Network analyzer interface. None has the Spectrum analyzer interface.

We would like buy the Spectrum analyzer interface (we have the HP141).

Somebody can do us offers about this device, or to tell us some site (WWW) where we can find it ?.

Thanks in advance.

Joaquin