Tektro R536 or R538 is good up to 57mm drop. If you're lazy and don't want to file the brake arm, then cut off about 1mm off the top of the rubber pad. You're not going to notice any drop in performance, because the calipers will still be able to lock the front wheel. Zero in on the area around the letter "FORWARD" on the brake shoes when you take the picture. External lighting will help with the contrast.