There are a few others you might be able to find,
there is a "Rescue 911" ambulance, chevrolet van you can often find on ebay, generally pretty cheap too.
Johan made a 1960's Cadillac ambulance you can also find frequently on ebay (not so cheap though).
The Joker Goon car is pretty easy to find, it can be built as a Gothom City police car but it wouldn't take much to make it a fire chiefs car instead, I think it is a 1977 Dodge Monaco.
If you are willing to use resin and/or do some scratchbuilding it opens up many more possibilities. There are several aftermarket companies with 1/24, 1/25 scale cab kits and accessories.
Not really kits but there several small scale emergency vehicles available and many like to kit bash these, there is some aftermarket available.
Code 3 is 1/64, Matchbox has a series in 1/50, Corgi is 1/43 and there is a fair amount available in 1/87 scale.
For the most part though unless you want to build European apparatus you will have to learn to scratch build and kit bash. It is not as hard as most expect.