@jetton@paradoxmo Goulet Pens has excellent selection, customer service, and customer education (check out their YouTube channel). Other good general stockists in the USA include Pen Chalet, Anderson Pens, Vanness Pens, and Endless Pens. If you’re looking for something specific, there may be better specialist retailers.
It’s also worth supporting a local brick-and-mortar retailer if you have one in your city.