In my endless quest to find a nearby shop that carries anything shamisen I came across McCabe’s Guitar Shop in Santa Monica - very well known but I had no idea they actually had occassional shamisen workshops …
https://www.mccabes.com/store/cart.php?target=product&product_id=1726
The description seems to suggest it covers a broad brush from sanshin to shamisen. Good chance I’ll attend the next one in July. Talking to a guy over there, he says they have one every few months or so.