My favorite on-line site for storage & organizational solutions that don't break the bank is
www.stacksandstacks.com
I just checked and they have Christmas Tree storage bags for $9.99 plus shipping. If you live in the USA (except military address, Hawaii, or Alaska) shipping will run you $5.70 for a total of $15.69. They carry two bags for $9.99; the one that is 4 inches longer is temporarily out of stock, but the shorter one is in stock.