I came across these replicas while searching ebay.....geezzzzz, even these are pricey! Might be a good alternative if you're building a car though.
http://cgi.ebay.com/adam-12-lapd-trio-lights-lapd-lights-vintage-police-/170598851893?pt=LH_DefaultDomain_0&hash=item27b87be535
http://cgi.ebay.com/adam-12-lapd-trio-lights-lapd-lights-vintage-police-/170598851893?pt=LH_DefaultDomain_0&hash=item27b87be535