I ran into a Candy Red GL1800 with a nice flashing brake light setup. Not the normal brake light on the spoiler.
The fellow said he had gotten it at Americade but doesn't know vendor and/or brand.
The setup alternates the two brake lights located on the trunk.
Each of those lights has two sections. The electronics alternates between the outer most lights and inner most pair.
I was a little more impressed with the effect than the normal flashing spoiler brake light.
Hope I made myself clear and that someone could give me a hint to find a supplier.