The Micropulse by Federal Signal is a popular and very bright small-profile surface or grille light. It utilizes 6 high power LEDs behind optics and is similar in size to the Whelen Ion. 
 
Purchase includes L-bracket for mounting.
 
Wiring: 12V DC, power/ground/pattern change/etc.
Mounting: Screw mount, L bracket included
Dimensions: ~5" L x 0.75" H x 1" D