We don't.

In our family we eat what we store and store what we eat, we always have 5-6 open buckets that we're cooking and eating from. We use the much less expensive snap on lids ($1.36ea, we re-use these too, btw) and when we have an open bucket of food we use Saver Lids, which cost less than $2.00 and can be used on all your buckets:

http://www.usplastic.com/catalog/ite...4281&catid=686

That said if you want gamma seals the best prices I've found are at US Plastics:

http://www.usplastic.com/catalog/ite...=searchresults

Good luck!