If you're happy with a buzzer on all the time with the indicators, you can get two and three pin indicator relays with built in buzzers - just remove old and put in new.

I have a buzzer with a built in time delay so it only comes on after a certain number of flashes, and it silences when the brake pedal is used. That required a bit more wiring/splicing.

"Y mae dafad ddu ym mhob praidd"
1972 4/4, 1981 MGBGT, 1984 FLHT1340, 1980 XLH1000, 1990 ZX10