I believe the most commonly found coupe glasses at cocktail bars are the Libbey 3777 (4.5 oz) and 3773 (5.5 oz). I recently purchased these online, and they're exactly what I was looking for.
The rub is that you have to buy 36 of them at a time. I suspect these can be found at restaurant supply type stores, though I've never cared to look since I just purchased them online and had them delivered to my door. At about 3 dollars per glass, I didn't view it as too big of a risk, and I'm very happy with the purchase. I ended up splitting the box with fellow LTHers.