There are some techs out there who can fabricate a key for you. I have an early 13 key clarinet in the key of A that is in the shop. The tech is going to make the left hand pinky key and a low G# key whenever he can get back to his shop. Not everyone does it but there are a few out there with the skills it won’t come cheap. I think he’s charging me $500 just for the two keys.