Simple! A long sleeve shirt, worn as an accessory. Displayed here is the reason I made it: I needed a short sleeve over a long sleeve for Dudley Landgraab here, and so I made it myself. It works with any top, and any outfit. Plus, it's CASTable! (1 channel) And it works for females, too! But their shoulders look a bit odd, for some reason.
Ages Teen-Elder, both genders!
It's based on socks, so if you want to wear it with socks, you're out of luck. Or you can change it with the CTU.