I have come accross this Opto Isolator Mini Board, supports 8 opto-isolators to provide a standard port conversion between a 3V output port to a standard 5V output
It also suggests that the price may not remain that low in future (Special Introductory Price), and for only 5 bucks you may as well grab one on the offchance it works. It isn't like you'd be losing out much if it didn't.