here's what I'd do:
D8 in sweater. Cut tiny whole in sweater to run the cord under the sweater, up your back. Wear a backwards baseball cap. Run the caps into the cap up your neck into the sweatband of the baseball cap. As long as you don't pull on the cable the fabric won't rub on the cap and make any noise. If the sweater has a hood, you can bunch the hood up to hide the cable.
You can arrange the caps on the side of your head so they are facing forward, or more towards the back like DIN or ORTF.
But there are many other ways