Tin Pot
Guru
I didn't know what a Wahoo was, which is explained by the fact it has something to do with fitness.
Assuming the magnet is a small button one, and as you want one on the hurry up, my suggestion would be to nip to Halfords buy the cheapest cycle computer, and use the magnet from it.
Looked like this was my route to success, got a deal for £4.50 - not too bad.
Got home set it up, picked up the spindle for the turbo to switch it over....the original magnet was stuck to it.