Trying to find a cheap way to sift rock with A Cat 950F

Hello,

I am trying to find a way to separate the fines from the larger rocks with a Caterpillar 950F with the beales quick coupler. I haven't found much luck finding a sieve bucket and I am going to try to build something out of a few pairs of forks. Can you think of any other ways of separating the material? Any thoughts appreciated.

Thanks,

Darryl