Look through the wrecking yards and see if you can find a 1977-1989 Chevy Impala Police Special. Don't know about the 1990-1996 versions; although the body shape changed dramatically, don't know if they made any big changes to the suspension. Don't think they did, but would measure any likely candidates carefully before taking them off.
Suspension should be the same design and the sway bars should fit and be fatter. Believe the option code on the civilian models was BF41 Sport suspension. There were even a few Buick police cars made in the early 80's; they should have pieces that work too.