I use a rack trunk with my dinotte 140L taillight. It takes a bit of creativity but it works nicely. Plus, since I use the AA version I can stick the battery pack in my performance pannier. My other options are my panniers or a messenger bag. I pick and choose what one to use depending upon what I have to haul and the distance.
The topeak rack trunk looks nice but I do not like seatpost mounted racks. Is there any option for normal racks? I do not see anything.