Looks like this one...
https://www.nilight.com/collections/license-plate-mount/products/nilight-led-light-bar-universal-license-plate-mount-bracket-heavy-duty-steel-front-plate-mounting-bracket-holder-for-off-road-lights-led-work-lamps-lighting-bars-2-years-warranty
I've got a few Mavericks we use as fleet vehicles for our security company. They have the actual keyed ignition and this double-honk happens sometimes when the driver door is opened. It is inconsistent, sometimes happening when the key is in the ignition and sometime when it is not. Not a good...