I've been away from Wah-wahs for 40 years but back than I was building copies of Vox. We didn't have proper pedals so I converted speed pedals from sawing machines.
The inductor is a critical component so after having wound tens of different ones and not hitting the sweet spot I tried a discarded recording head from a tape deck. Bingo! There was an electronics surplus shop where one could buy tape heads that didn't pass quality control at the factory. I bought a bucket full for next to nothing.
So, get a few old tape decks at a garage sale, remove the heads and try them in your wah-wah. You'll be surpised. Heads from cassette recorders have to low inductance but ones from 8-tracks could very well be just fine.