The core elements of the character: the bomber jacket, the power-pack, and the goggles.
To create the jacket, I used an old, lined, brown Lands' End jacket (or was it L.L. Bean? Who can really tell the difference, anyways) and turned under the hood to make it look like a collar. Then I sewed on the patches we bought from Serephitic. (If I hadn't found those, I had planned to draw/color the patches, seal them in clear Contact paper, then pin them on.)
And ski goggles to finish it off.
The finished Tracer costume was Awesome.
And the really great part was that once it got dark the power pack was a great combo flashlight and keeping-track-of-child device. My son was totally jazzed.
The two things that made him a little shy were that 1) he was dressed as a girl (to which I responded that no one knows who Tracer is, much less her gender) and 2) answering the question "Who are you dressed as?" It was a mouthful for him to say "I'm a videogame hero named Tracer from a game called Overwatch that is in closed Beta right now." So I think some folks thought he was a WWII bomber with a big Ironman light on his chest.
And that was OK, too.