I've flown with my bicycle from US to foreign country more than half a dozen trips (not counting Canada). I've always been able to get by with an airline box or once with plastic bag coming back from Amsterdam. It has done fine so far w/o extra case.
I'm also currently overseas, on business instead of touring unfortunately. However, I did bring along a mountain bike on this trip so I can spend some weekends exploring the countryside. For the first time in over 30+ flights, including domestic travel, I found there were no boxes at a US airport where I departed (Portland). United Express made an exception and my connecting Lufthansa flights don't require a box. The bike made it through fine, with front wheel slightly out of true, but nothing I couldn't fix.
So depending on how often you plan to travel, you might be able to get by with bike boxes purchased from the airlines. Depending on the overseas country and whether you are doing a one-way leg, it can be useful to either save your box or find a replacement at local shop before your departure. I've bought them at the airport (Australia, NZ, Netherlands) and bought them locally (Malaysia, Russia) and saved them (India, China).