WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
Building, troubleshooting and testing of these amplifiers should only be
performed by someone who is thoroughly familiar with
the safety precautions around high voltages.
I have various fixed air-gap toroidal chokes. Please PM me for more info. I can send within EU only, however.
If you in USA/Canada, you can ask Micrometals where you can order them. Micrometals is manufacturer of iron powder toroidal cores.
I'm not a manufacturer. I have spare chokes because of minimum order qty exceeded my own needs. Chokes made in Eastern Europe along with other custom products.
Sorry, its against company policy I'm employed by to distribute abroad suppliers of spare parts and raw material.
You can contact another company, Tauscher in Germany, which can make custom chokes with iron powder cores with distributed air gap. Tauscher Transformatoren GmbH
And any other company which source iron powder cores from Micrometals.
Fixed air gap toroid GOSS cores/chokes are not standard products, they made only per customer specification/order. it is very unlikely any factory will mess with a couple of pieces.