Sending a package across the world?

So I have this internet friend, her name is Tara and she lives in australia. I live in California. And I went to a 5sos concert in July, and after the concert people were outside selling shirts for cheaper price, so I bought one for her in her size without thinking about how the hell I would get it to her lol. So her and I talked and we were like hey what if we sent each other packages. So I was wondering how much it would cost to send a package from here to New South Wales. It wouldn t be that heavy. Maybe like two pounds. I would just sent a t-shirt, some photos, a handwritten letter, and maybe some other few light gifts (like a bracelet or candy) or something. I would probably have to pay to ship it and stuff and was wondering if anyone knew how much it would cost