try writing a letter to the company's saying how much you love their product, and would like to show your love by wearing one of their shirts.
it can't hurt, my cousin got sent a box of Smiths' chips 'cause he felt like writing them a letter.
I've even done some leg work for you and here's Redbull Australia's mailing address:
838 Elizabeth Street
2017 Waterloo NSW
+61 2 9023 2800
+61 2 9023 2900