洋气 does certainly mean "fashionable." But so do 有形 in Cantonese, and phrases such as 时尚. Thus "fashionable" as a translatioin seems a little generic here.

So I wonder: Isn't there a word or phrase that is closer to 洋气?

I note that the word 洋 also means "foreign," and --- to me --- the phrase 洋气 is more than just "fashionable"; It means "in vogue" or "chic," both of which are from the French and thus capture a bit of that foreign + fashionable feeling...