Check this link. May be you can find your item over there. Good luck.
stumbler wrote:
Stumbled (hence the handle), knocked over tripod, broke the plastic ring on front of 10-24 lens. It is affixed by 3 screws to lens housing. Doesn't seem like it should cost a lot to repair, but the offers are high. Cannot find a parts diagram, or anyone to talk to on a Sunday. Suggestions?
Thanks.