If you are in the United States, you are giving your money to Hershey for Kit Kat; it is licensed from Nestlé based on a previous deal with the original owner of the brand. I don't know the exact details of the contract, but it appears that it was a lump sum payment which means no money goes to Nestlé for Kit Kat sales in the US.

Still, Hershey is not much better, and this factoid is irrelevant if you are NOT buying the US version. Similar options include Tim Tam, Double Time, Dido, Trader Joe's Wafer Cookie, Milka Leo or Choco Wafer, Little Secrets Crispy Wafers, and any number of other generic chocolate wafers. You can also make your own: https://www.inthekitchenwithmatt.com/homemade-kit-kats.