For the OP, it's doubtful that an Otterbox belt clip will work. They are made for the Defender to "snap" into through the use of notches built into the side of the defender case. A more suitable option may be one of the Seidio holsters as they use a spring clip latch. You may want to look at the Seidio Dilex holster.
Another option for holsters are offered by Simple Be. A friend at work got one and likes it a lot. They have stock sizes and also offer custom fitting.
http://www.simple.be/holsters/