Thanks so much for all the information!
I'm a new member and fairly new to Cosplay in general.
I've been doing my own research (such as it is) on the Hopper costume and I'm pretty sure the shirt is the Flying Cross 19w6604.
As pointed out this style has the non-pleated pockets.
Comes in "tan" and "silver tan" and as is common with screen shots the exact colour of the original shirt is difficult to determine. (EDIT: silver tan is correct.)
Not sure, but the 19w6604 may no longer be in production. (EDIT: it's in production but also numbered 40w6504.)
His flag patch isn't reversed, which I think is probably correct to period. (EDIT: The wearing of reversed flags on the right arm dates to a US Army regulation from 2003.)
I've had a devil of a time trying to pin down the exact colour of the hat. In some shots it looks only slightly darker than the shirt, while in other shots it looks much darker. Some shots show taupe, some chocolate, some olive drab, some walnut.
It's basically a C-Crown or Teardrop Crown fedora, seems to me. Possibly the closest hat in production is the Stetson Stratoliner or Open Road in the colour Stetson called "Caribou".