I just spent 2 hours looking at pretty much every site that Google brought up, although there are some great prices, Your Paper Source - ShopAnchorPaper.com
which is what Lisa Loiselle, said is pretty much the best price. It breaks down to 5 cents an envelope... and have the square flap. (which I prefer) I look forward to seeing them in a couple days. I hope the quality is as good as they look.
Just thought I would share my 2 hours of work with all of you!