Keep your eye open and you'll find GREAT prices on the gamma lids.  I've never paid more than 6 or 7 dollars for them. I consistenly find them on sale at Harmons or Maceys, and even once at Wal-Mart. In fact, Macey's had them last week for only $5.99.
Remember, don't buy the buckets. You can obtain them for free for the asking at Costco or grocery store bakeries. To clean them out just use a bleach/water solution...no other chemicals.  These buckets are food grade so they are safe to use for just about everything. (I wouldn't use them to store oats in though, because oats need a sealed environment to last the longest.)  I also wouldn't bother using an oxy packet in these but since they are porous, I wouldn't waste your time.