Go to this thread from a Ninja 250 forum I also frequent, it has a lot of good suggestions -
http://www.ninjette.org/forums/showthread.php?t=12425&
The ICON Squad II (2 videos on there) looks like it will hold everything you may ever want to carry, but there are a few others on there that will also carry a helmet.
Also look at this thread -
http://www.ninjette.org/forums/showthread.php?t=35505
Here's another idea -
http://www.motorcycle-superstore.com/1/ ... kpack.aspx
You can go anywhere from $8 at Walmart, to $39 at Lands End, to $125 for the Icon Squad, to $160 or more for others, and everywhere in between. It's only money, but most of these will last many, many years and actually provide some crash protection too. Good luck in your search, there are too many choices to make an easy decision.