Katrina, There are not many options. The materials that the rock guard are made of are not manufactured anymore. People frequently loose their rock guard while on the road. It flys open, and is gone.
Tom Young sells Trillium
parts on this web site:
He sells a rock guard, with hardware, for $485 usd, plus shipping. Not the original look, but functional.
I may be interested in purchasing your broken one. PM me.