[Elecraft] Common mode chokes

[Gary]

Hi,
I have an inverter generator producing S9 noise on 3.5Mhz, and S7 noise on 7Mhz. Higher frequencies are clear.
If I were to use a trifilar wound choke on the lead from the generator, what would be the best mix...43, 77 or?....
I can source ferrite cores here in VK, whether I can obtain what I will need is unknown but likely. Failing that, Mouser?
I spent a lot of time searching the web but unsure still.
If the learned group could help out with advice it will be greatly appreciated.
Regards,
Gary