Watch some of the real show. Miracle Day was a complete retooling and the costume was awful.
EDIT: To clarify, the holster and VM in Miracle Day were terrible work. The holster was an attempt to make a classic style flap holster that could hold a semi-auto. Not very good either, because I've done a custom like that before and it didn't turn out looking anywhere near that much like a map case. The VM was just a failing to reproduce the original, which isn't surprising because the thing is complex. The pants were too dark, the red suspenders were not a good choice IMO and the coat was just a stupid decision.
Anyway, it's definitely not a USAF or RAF shirt. It shares characteristics with each, but it's neither. (at least in the original series. It'll be a while before I watch Miracle Day again.) Maybe they did use one or the other for Miracle Day, and if so that's cool for people that want to use it. I personally don't want to.