My son would like a top case on his RD to put helmet, boots and cordura pants in when he rides to school next spring. I thought I better start looking early, since I suppose it's not the most common bike to put stuff like that on... Does anybody know if it's even possible? The main thing is that it's lockable, since he fears that they will steal anything that's not locked in, so a soft bag won't work.

Anything and everything is possible!, sometimes you just need a bit ingenuity.

You don't mention which year it is so i guess its similar to this one,

http://www.2dehands....x-84589864.html

As you can see its got a rear rack fitted and if you can get a rack then most top boxes come with universal fitting plates to take a top box.

and if you can't find a rack then a rack can be easily modified with the aforementioned ingenuity!

I modified a rack for another bike and put a Givi box on it with its universal bracket for my DT