Here’s a gadget that will keep a half of a banana fresh.
NANA Saver™ Banana Holder Eliminates waste so you can enjoy half now, and half later. Keeps a sliced banana fresher, longer by reducing exposure to air. Hinged banana shaped body with tiny teeth grip sliced bananas firmly in place and flat plate presses snug against banana face to minimize air contact.
Only $2.98. Personally, I just fold the first half of the banana peel over the exposed fruit, although eating only half a banana is a rare thing at my house. dd -via the Presurfer