For junior girls the pocket is located on the side of the shirt. The hidden slit in the back of the pocket also allows for all tubing to be concealed. T-shirts with pockets for your pump. Pump pockets for your insulin pump,creative ways to keep your pump secure. Ways to hide your insulin pump. Undershirts have numerous uses, they can be worn as an undershirt or a tank top. They are also great for sleeping in.