I hear ya, man....

..no pun intended. Lost all my hi freq hearing piloting choppers in 'Nam in the late 60s. This site caught my eye,
Electrical Acc. but I haven't tried any solution yet myself. Most of my loss is 4000-8000 Hz. The buzzer on my boat is a small piezo bundled with the ignition wires right behind the switch. There seems to be lots if choices to try when I Googled "12 volt low pitch buzzer." Good luck to you.