I've decided to go with 2 unmarked sheriff cruisers, somewhat similar to what is there in 11john's photos. I won't add more until we can have full confirmation on what they would have used.
I was not able to find the specific brand or model for the weird steady burn beacon. As a result, I've decided to have a bit of compromise. The unmarked Malibu will have a steady red spotlight but with a Federal Signal Firebam on the roof for 360 degree coverage.
The lighting on the Caprice is a mix of various 2000's sheriff unmarked units I've foud.
On the topic of civs, I have started making edits of the existing models and turning them into new variants with new designs, for different cars: