Hi Wenie.
I agree with flatulent, this 120dB will be difficult to get using active devices.
It maybe possible but it will not be easy.
I have another idea that could help to solve your problem.
I vote again for the RLC series network to ground. But this time I propose something different for the synthezis. Instead of using Antoniou GIC you couls use switch capacitor technique and keeping unit gain ( no need for opamps or active devices).
You should build an convensional air core inductor to get rid of any kind of distortion.
And I believe, for the capacitor (or the resistor), a good solution would be to use a switched capacitor. A good quality capacitor, polystirene for example.
And maybe simple inverter switchs like 4066 would do the job. Or if something better is needed maybe mosfets like BS170, BS250, could do it....
We would have to search for a good swtched capacitor (unit gain) configuration to realize this transfer function. (notch)........
The opamp you found could be used as buffer......
And now a question....What would be the configuration to implement?????
S.