Keep an eye out at Ōi Keibajō — you're sure to find a great travel trinket in one of its many stalls. After you've admired the wares, grab a bite to eat from one of the food vendors.
If you're staying a while in Ginza, Ōi Keibajō is a good place to start your exploring. This community marketplace is one of numerous attractions that'll keep you on the go here. Tokyo Skytree, Tokyo Tower, and Tokyo Imperial Palace are also waiting to be discovered nearby.