A company called iTAC makes one for a G21 that will fit your G30, but it'll be a bit long.
Those were my favorites when I had a G30.
"An armed society is a polite society." — Robert A. Heinlein
"After a shooting spree, they always want to take the guns away from the people who didn't do it. I sure as hell wouldn't want to live in a society where the only people allowed guns are the police and the military."
— William S. Burroughs