Scientific Atlanta Reverse Injection Filter (65/88 MHz split)

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I am looking for assitance with locating  a Scientific Atlanta reverse injection filter model number 548531.

Scientific Atlanta are no more, they have been acquired by Cisco.
Cisco can supply the filter but only if I am happy to purchase 100 pieces as a special production run.

This is ofcourse a bit difficult to swallow.
The filter is used to inject signaling tones in the reverse direction ( towards mast head).  May be someone knows of an MATV /CATV company whihc might still have some old stocks or may be a circuit diagram and or  bill of material so that I may be able to build a filter.
The filter consists of a ( i suspect ) power passing stage a reverse injection coupler and a may be diplexer /low p[ass/high pass filter.

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Any takers?