I used ebay when I bought mine. It was kiln dried but in rough dimensions. If you want dimensioned lumber, I'd say Rockler or Woodcraft is your best bet. Be careful not to get veneer as some sites aren't very clear as to what they're selling.
You don't really need to line a coolador, boxes are enough. Though I do understand how intoxicating that smell is and how nice it is to have it.