It seems to be one of those words, like mężczyzna, that's considered masculine, and takes masculine pronouns, etc, but ends with an a and declines like a feminine noun.
Oh no, wait. Turysta is male, it's an exception. That's why it has an ą in instrumental. Like mężczyzna, too. The female would be 'turystką' as already written here. I'm sorry, already a bit tired. I'll give you the lingot back