I'm a moron, I can to do it in Photoshop so easy...

1. Open your .png file in Photoshop and copy it merged into a new file.
2. Add a new white layer under the image layer.
3. Press W to select the Magic Wand Tool.
4. Set the Tolerance to 0 and uncheck the Anti-Aliased option.
4. Select the image layer and click on any white area.
5. Hit Delete.
6. Save for web... voila.