I think a new pair of sunglasses definitely calls for a custom case...
Here's how to make one:
Choose an exterior and interior fabric, as well as a solid black for the lens and a fabric for the frames. You can use fat quarter sized fabrics, or just scraps you have laying around.
I found a cute template for some "hipster glasses" here. I shrunk them down to 75% of their original size when I printed them.
Lay your sunglasses on the exterior fabric and decide what size you'd like your case. Don't forget to add 1/4" to each side for seams. My glasses are quite small so my case only measured 6 3/4" x 3 1/2" to start. Cut two from your exterior fabric and two the same size (minus 1/4" on length) for your interior.
(ex. instead of 6 3/4" in length, you'd cut 6 1/2" in length for the interior fabric only)
Use the image your printed to create an iron-on appliqué using Heat and Bond lite onto one of your exterior units. Press fusible fleece, cut to the same dimensions, to the wrong side of your exterior units.
stitch your exterior units right sides together leaving the top open and using a 1/4" seam allowance. Repeat with your interior units, but leave a 2" opening at the bottom in addition to leaving the top open. Clip the corners to eliminate bulk, careful not to clip into seams. Flip exterior or case right side out and push the corners out with a closed pair of scissors or a turning tool to create nice points.
place exterior case into interior case so right sides of fabric are together, lining up side seams. Handstitch around the top through all layers of fabric and tie off. I like to sew a few times around, to create more stability, because my hand sewing isn't the smallest.
Pull the exterior of the case through the small opening in the bottom of the interior and turn the interior right side out. Hand sew the small opening closed, push it to the inside of the exterior and press with a warm iron.
Now, slide your favorite shades in, and you're new case is ready.