For years I carried all of my riding stuff in a regular backpack, put inside of a trash bag. It would end up smashed down behind the passenger seat or thrown in the back.  All that really got me was a muddy backpack, wet maps, dirty tools and a destroyed sandwich. That is what lead to the design of the Haversack 15. 

It is a 15 liter dry bag made out of the same heavy duty stuff as white water rafts. It has the exact buckles as you can find on life vests.  It also has the added flexibility to be mounted to the roll bar, safe and out of your way.  They are simple to use.  Load up your gear, roll the top over on itself a few times and buckle closed. Your stuff will be kept dry and free of mud, dust and sand.  Included is an adjustable shoulder strap for easy carry to and from your machine. There is even a zippered window pocket on the front for your phone.

Check it out.