Based on the publication of Matthias, DD1US, I bought from him one of these TMT H3930 isolators - Thanks Matthias for supporting the community!!!
Here are my measurements taken with my miniVNAtiny and vna/J 3.4.8:
S21 
S12 
S11 
S22 
For reference, here the naming of the measurement (from wikipedia):
S11 - Input matching at transmitter side - worst SWR is 11.2:1 @ 2.4GHz
S22 - Input matching at antenne side
S21 - Transmission loss from transmitter to antenna
S12 - Isolation from antenna to transmitter