This topic comes up periodically.
There is a schematic for a 125kHz filter in Fig. 28 (p16) of the datasheet for the National Semiconductor LM1893 (an obsolete FSK powerline modem chip).
The chokes need to be rated for the current they'll see and the capacitor should be X2 rated.
...and since these caps are such *precision* parts, (10 to 20%), you might build yourself a cheepie bridge so you can pull turns off the toroid to adjust the thing to be close to resonant where you want it.
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