(Author here) I ended up buying a bunch of the components, including all of the passives, at LCSC. Notably the Cypress chip was much less expensive there too. Here's a link to the resistor network part I bought:
On a side note, I mentioned in the video that it was super tedious to solder all of the passives. If I were doing this again I would strongly consider doing the JLCPCB/LCSC thing and having them populate all of the caps/resistors on the bottom side for me.
https://www.lcsc.com/product-detail/_UNI-ROYAL-Uniroyal-Elec...
On a side note, I mentioned in the video that it was super tedious to solder all of the passives. If I were doing this again I would strongly consider doing the JLCPCB/LCSC thing and having them populate all of the caps/resistors on the bottom side for me.