I'm sure this has already been settled, but what I did was take a t-shirt that fit a little snug. Then I cut it apart, making four pieces, front, back and sleeves. I then modified the sleeves to look like they would work. Then I cut the pieces out of the material and sewed them together. For the back I made two pieces, basically so they would overlap and velcro could be added so that it would stay secure. No one sees it because of the back armor.