Just a note. I ordered 2 Google adapters in mid July, checked the order status a few days later, and back then the expected delivery date was in October. I think like the 2nd week. So I cancelled that and bought these for $19.90 for two from Amazon.
https://www.amazon.com/gp/product/B07DY8B9GR/ref=oh_aui_detailpage_o02_s00?ie=UTF8&psc=1
They work fine and they're better because they actually arrived shortly after I ordered. Since Google charges shipping on small orders, it was going to cost $23 something for two and I'd still be maybe 6 weeks away from getting them.
My fear is Google is not really keeping them in stock because they're putting either a regular 3.5mm headset jack on the Pixel 3, or there will be a DAC so that the cable doesn't need to have it.