I use a nice small, soft shoulder travel bag that can be bought in any department store. It holds the knee board, extra charts, AIP, copy of the airplane manual, extra pens and pencils (the ones I usually use are tied to the kneeboard so that they don't fall to the floor), rulers, etc etc... I can even fit the headset into it if I want!
No, don't go for the black leather pilot bags... very unpracticle, not too mention appearing like a
Westy