What's wrong with the cardboard boxes that you can get for free from any bike shop?
There is nothing at all wrong with boxes from a bike store, except they are often much smaller that the boxes United Airlines sells. My touring bike has a front rack, a back rack and fenders on both wheels. I also carry three water bottles. With the United box all I had to do was remove the front wheel and pedals and turn the handlebars 90 degrees. With boxes from the bike shop I had to remove the front wheel, saddle, pedals, handlebars and racks. Depending on the box, sometimes I had to remove the derailer.