I've also purchased mine at Big Lots...giggle...when they carry the Martha Stewart stuff, they will usually sell the invitation sets for $2 for 40 invites or so. Last time they did it, I bought 7 boxes so paid $14 and had 280 envelopes...sorry, I did toss the invites, I only wanted the envelopes. I still have 5 boxes left.
My Big Lots had a few wedding ones left when I was there last weekend. You might try it.