I have something similar installed in my Tundra. It's a Galls police siren, air horn, PA system. Had my stereo guy build a fiberglass surround to flush mount in in my dash below the temperature controls. Not the best pic, but hope it helps. I can take more detailed pics and email them if you'd like.
2007 Tundra crewmax. Lowered 2/4.5" with Belltech struts and Tundra Racing flip kit. 26" Lexani LX7 with 305/30/26 Pirelli tires. Color matched Paramount grille, door handles, side mirrors, rear bumper, and tailgate handle. Phillips 6000k HID kits in headlights and foglights. V-Leds interior and exterior. Hella celis tail lights. Flowmaster Super44 dual in/out exhaust. Upgraded the JBL stereo with a few things and added a bunch of sound deadening.