Where to find ferrite toroidal coil?

Ferrite toroidal coils can be found at electronics supply stores, both physical and online, such as Digi-Key, Mouser, or Newark. Additionally, they are available on e-commerce platforms like Amazon and eBay. Local hobby shops that specialize in electronics or DIY projects may also carry them. If you're looking for specific sizes or specifications, checking with manufacturers like Fair-Rite or Amidon could be beneficial.