I ordered them from eBay seller "memorablewedding." They had the best prices I could find. Including shipping, I believe it was about $38 for 300 cocktail napkins. We did 150 black and 150 aqua.
A totally unnecessary expense, for sure, but given that we're spending next to nothing on decor at the reception, I felt like it was another one of those special touches. And they were relatively inexpensive, too. We're going to split them up... some of them will be passed out with drinks at the cocktail hour, and the rest will be on the cake table and given out when cake is served.