that's generally how it works. for instance, you snap the small plastic collar on your gearstick.... looks like it'll be worth no more than 50 cents to replace, then you find out holden only sell the whole gearstick assembly for $350.
your best bet is to either go to a wrecker and get lucky, or find the manufacturer of the light (probably valeo or carrello) and see if you can order spares. also check ozeparts.com.au