Funny you should mention it. I'm going to have to ship a bunch of stuff next week, so I went dumpster diving behind music shops this past weekend. The bin behind Mother's music was a treasure trove. They had everything - guitar boxes, amp head boxes, cabinet boxes, packing materials. Everything from tiny to huge. I wouldn't bother asking the sales guys. They know they're not getting commission on a free cardboard box. Just go to each of the shops and check the bins out back yourself. Also, if you don't find anything today, check tomorrow. That stuff gets turned over pretty quickly.