third break light replacement with cap/topper

I bought a used cap a few weeks ago, purchased it at night and slid it on in the dark. the next morning I realized that The cap has indents for a third brake light but is about 1/4in too small. so the whole cap is off kilter due to not being flush with the truck. what are my options here? The cap is fiberglass. I tried poking around online to find flat/flush third brake covers but no success. suggestions?
uploaded some poorly lit photos but you can kind of see it pressing against the brake light.

 

Take the lens off and fab a plate to go over it. It's clearly not usable anymore, so remove it and cover it. Tin snips and a $12 hunk of sheet metal from ACE hardware (or a beer can, if you're in a hurry) lol.
Zim

 

This is probably your only choice, or get a piece of lexan. Take the bulb so you won't have a bright light shining when you press the brake pedal if you use lexan.

 

slide the cap a few millimeters backwards

 

It could be that the cap is actually designed for a different vehicle. I know that Toyota pickup (before the tacoma) caps were a little shorter. Since yours is a high-rise cap, then it's kind of hard to tell.

You could also shave down those parts on the cap, then get a fiberglass repair kit to seal it up.