I second costco. They normally have decent vests there. Mine is a HO Costco special, very nice.
I have a friend who works at Costco corporate and is in charge of screening all product any manufacturer wants Costco to sell. They don't just negotiate price, but also negotiate quality. They won't accept anything less than the normal retail quality, but often times will kick the product back if they want it better quality than the retail version that is presented to them, normally at the same, or better price point.
A good example is my HO life vest. It is the same, but with different colorings as HOs vest that goes for $70-80, but is for $40. They didn't want to just carry the standard at the same or discounted price point, they wanted higher quality.
I actually got lucky and found mine on the side of the road one day at work, it was the beginning of the season, in almost new condition, and exactly my size. I have been happy with the performance 3 seasons later.
EDIT: I just checked Costco's site and they don't have any listed atm, it might be different in store though.