GT Distributor has wig wag controllers that will work on the headlights or any auxilliary lighting as well as sirens, strobes, etc - some items such as red/blue strobes and lights can only be sold to those with credentials.
http://www.gtdist.com/

I used a flat 100w speaker that is not listed in their catalog to fit behind the grill. Their standard one would fit facing down though. Lots of controller choices including ones with PA capability but I thought those might really get me in trouble....