The rear reservoir always seemed to be vulnerable to me.  I know of no product offered to protect the reservoir, and after working on the design for a few hours, I figured out why there was nothing on the market.

As usual, I started with a manila folder and a pair of scissors.  My first design looked like this...

... I didn't like it.

After a few more tries, I finally settled on the following design made from 0.0623" (1.58mm) aluminum...

The problem is that there is really no where to mount any sort of guard.  While my design may offer some protection, I'm really of the opinion this is a strictly cosmetic farkle.

In order to mount the guard, I obtained a longer bolt, a spacer (which I cut down to about 7/8"), and a flat washer.  Using the washer on the original bolt, the order of assembly is shown below...

Basically it goes in the following order: new bolt, stock washer, guard, spacer, new washer, and finally the reservoir (not shown in the picture above).  Once everything is assembled, the screw then goes through the mounting hole in the reservoir and screws into the original reservoir location on the motorcycle. 

And what do you know... it looks good on a Dakar too!