Silage Bags aren't cheap ---- Maybe you can find a farmer with some leftover. I noticed my neighbor filling his silo today -- next will come the big tubes (he makes 3 or 4 about 12' Diameter by 80' feet long. He said each one cost about $25. He buys bulk (5000' for $175.00). The other alternative is individual bags they put the big bales in --- they come flat but again in a box of 500.