My husband got this little handlebar bag for his Speed Triple last year and it's the *perfect* little bag. All the motorcycle needs is a handlebar to attach the bag with velcro. Minimal installation.

The Giant Loop Zigzag Handlebar bag retails for $55 and works on a variety of motorcycles including dirtbikes, cruisers, tourers, nakeds and classics. And it's just large enough for essentials: wallet, smartphone, keys, chapstick. Although i'm able to add a couple more small things like my sunglasses and garage door opener. I would call it water resistant since the zippers aren't sealed, so be sure to throw your wallet and phone into a tough little LokSak first.