Army PTI Training Jacket
In the movie SkyFall, James Bond wears an Army physical training corps PTI training jacket with an SIS insignia under the left chest pocket. The jacket can be spotted in the teaser trailer during the interrogation scene and in the other trailers in the shooting range scene. It is not known which company made the jacket, or if it was made or adjusted by the costume designer. PTI Training Jackets are made for the Army Physical Training Corps. PTI stands for Physical Training Instructor.
A good place to get one would be Joint Services Clothing, a British company that manufactures officially licensed clothing and delivers directly to the British Army. A similar jacket can be ordered on their website for £30.00, and you can even have a Bond inspired SIS insignia embroidered on it. Also available is a long sleeve shirt with the logo. The insignia has been updated in December 2012 to a more similar insignia as seen in SkyFall, order that one here (it's different from the one pictured on the left).