Of all the things I thought I'd learn to deal with while making Peggy costumes, car wrap vinyl was not high on my list. However, in my quest for closer to screen accurate sunglasses, that's what ended up happening.
I can't take credit for having figured this out. I got the idea from the very talented Adria in the Agent Carter Cosplay Community, but I still had to figure out how to do it. I used the guide here, which happened to be quite accurate. Since I wasn't doing an area too large, it worked really easily. To recap:
I took one set of not exactly SA, but better than the other pair I owned, sunglasses that had nasty polarised lenses together with a light smoky car headlight vinyl tint.
First I cleaned the lenses.
Then I peeled the two coverings off of a piece of the vinyl that was large enough to cover the lenses with a bit of excess.
Both the lens and the sticky side of the vinyl got sprayed with water. This helped the vinyl go down with less bubbles.
Then I kind of squeegeed the water out from between the two layers after I put the sticky side down on the lenses. I found that I had to hit it with the hair dryer to get the vinyl to hug the curve of the lenses. I took an X-acto blade to carve the excess vinyl off of the lenses.
In the end, I actually went for two layers of the vinyl as I thought the polarised finish was too obvious with just one layer of the vinyl. If I'd bought a darker vinyl, I might not have needed the second layer. This was slightly more difficult, but not significantly.
Actually the hardest part was getting the lenses back into the sunglasses without the vinyl pulling back. I had hoped to push the lenses in from the back, which would mean I wasn't pushing the vinyl up at all, but despite heating the frames it just didn't want to work. So eventually I had to push them in from the front which meant that a little bit of the vinyl pushed up at the edges.
It ended up being just fine as I took out the excess with cautious x-acto cuts.
In the end, I was pretty happy with how they turned out.