From the fine print on the back this looks like a MS charger marketed in Japan. I'd guess it's probably a safe bet.Took a look online and this seems to be the best option I could find:
Amazon.com: Dragon 48W 12V 3.6A Power Adapter Charger For Microsoft Surface Pro 1 Pro 2 and 10.1 Windows 8 Tablet PC with USB charging Port: Computers & Accessories
Does this seem like a mostly safe bet?