I used to use an Abus Granite Ulock and carried it like this.



I later changed to lock and chain in order to have a greater variety of things to chain it to. In order to keep the weight down I used a Pewag 7 mm square link chain with a Viro lock. I used a 2'-6" chain with an old tube around it. Weight is 2 pounds and 2 ounce which compares well against a U-lock. The Pewag is hardened to 63 Rockwell which is equal or better than the best bolt cutters.