I'm surprised that tubetops are not more popular. Especially, with women. Go to tubetops.net and use your imagination.
Order the spandex or cotton version. When placed on your body, instead of having the top of the tube just above your chest, pull the whole thing down so that the top of the tube is at your waist. Cut a hole and pull your pouch through it. Now pull up the bottom of the tube and you have formed an envelope.
Cost is between $10 and $20 each.