How to pack speakers w/out original boxes?

Help! I need advice on how to pack speakers,[Dahlquist 9c's], that don't have their original boxes. Speaker dimensions, Height: 23in., Width: 15in., Depth.: 12in.. Does anyone sell boxes big enough to ship these? They weigh 55lbs. each. What other packing materials should I use to protect them? Thank you in advance for your experienced Audiogoner wisdom! I'll take any advice that you all can give me.

Dave