6th gen nano hardware issue

My 6th gen nano has a hardware issue. The volume up button is physically stuck in the down position, so I can turn the volume down, but never up again.

I took it to the Apple Store, and one of the staff told me that my nano was still under warranty until the end of August. I went back a couple of days ago (in July) and was told that the warranty on the 6th gen has expired.

I can't get information about my nano on the Apple Support site, because whenever I enter the serial number of the nano into the window, it tells me to use a valid serial number.

Where do I go from here?