I am not sure if I can recommend getting any accessories in a brick and mortar wireless store due to their markup but if you need an emergency charger, dock, case, or such this could be worth checking out. T-Mobile sent out a tweet this weekend linking to a coupon that offers up 30% off one accessory in stores. It is valid until January 31st so no need to rush into the store.
You can find the coupon here from this tweet. Thanks Tashanna for the tip via TmoNews