Liveaquaria/Dr. Foster & Smith is considered one of the best in the US. The main drawback is the cost of shipping.
Thanks for the info. I know shipping is expensive, but I've been to or called 20 local shops and no one has them. I wonder why? I'm still trying to see if someone local can special order and if that would be a better deal. . . Anyway, it'll be a while because I'll have to get another small tank and cycle it before I could get a puffer - wouldn't want him to eat my neons! Good to know liveaquaria is a viable option though.
Not knowing where you live you might want to investigate a few of the closest major cities. Even if you spend the same amount of money in gas as you would shipping, I would feel better about driving 100 miles to find the right fish, see it before I buy it, and have it in my tank in a matter of a few hours.
I have driven 4+ hours one way to get the fish I wanted - and they have all survived.
I have also done mail order, and find that the smallest fish and/or juvenile fish do best. I have ordered mostly baby angelfish.