A pouch or purses is a small bag that is typically attached to a belt. Pouches come in many different designs and can be made from a diverse range of materials: leather, fabrics (such as brocade, wool), grasses (woven).
Pouches in the Manesse Codex (14th century)
Pouches in the SCA
Pouches may be used to store items such as your authorisation card, money, keys or food (for when you get bored during court).
Fabric sunglasses cases or any other drawstring bag, often work as a pouch until you make/obtain a more period pouch.
Women with wide skirts can have a nifty hidden pouch.
After putting on your underdress, tie a non bulky belt around your waist. Anything that doesn't stick out too much or cut into you is suitable, such as a length of braid, wide piece of ribbon, or cord. From this tie another thinner ribbon or cord (or even string) to the side of the belt, to hang down approximately 50cm. Tie your purse to the string, preferably in such a way that the drawstring holds it closed. The pouch should hang below the knee, but above the ankles, and if you get the spot right, it won't clank against your legs during normal walking. The pouch should definitely not tangle up your legs, and should be fairly easy to reach by bending over a little. You can cut thin slits (called "fitchets") in your dress to make it easier to access your purse. Some later period purses were worn quite high near the waist on a belt under the dress, and accessed by a pair of fitchets. These were called pockets.