I find a small backpack type to be the best. Plenty of compartments for charts, sunglasses etc. Headsets etc can fit in main compartment.
Useful thing about these is, that they can be fastened to the passenger seat by the shoulder straps. Rear of the seat if you have a front seat passenger or front of the seat if you dont. Thereby remaining accesible throughout your flight.
Also has the advantage of making it easy to carry your kit if like me you often travel to the airfield by motorcycle.
A further advantage is that they soon look shabby and do not have a negative affect on street cred.