Need to find a cheap source of R-134a

Hi, I will need to buy about 200-300 12 oz. cans of R-134a very shortly. I
don't want the 30 lb. cylinders, but individual cans. The brand is
irrelevant. I usually get them at Sam's Club for about $25 for a case of 12,
or at Wal-Mart for about $3.25 a can, but neither store has these since it
is still winter. They won't have them until later this spring.

Pep Boys wants around $5-$6 a can, but that is too expensive. Does anyone
know of a cheaper source?

Thanks!

Jenny M.