LBS usually have loads of nice bike boxes for you to have. Pretty sure they like you taking the boxes, saves them from the hassles of recycling them.

A few things to mention is you might have to go to your LBS a few days in advance and let them know your looking for a box to use. You may be looking at a time right after they took out the old boxes and they'll need to save one for you the next bike they build or is suitable enough to package a touring bike. Another thing is get the biggest box you can get that is OK for the airline. My last boxing up job was hell as I had a box a little small for my bike (90% of the bike had be disassembled)....Also don't forget you can throw most of your touring gear inside the box. Panniers can be used as protection for your bike