We found 1 Reddit comments about The Gorilla Screen Soil Sifter. Here are the top ones, ranked by their Reddit score.
You could sift it. This is expensive, but you can build something similar really cheap with a couple 2x4's and some 1/4" or 3/8" screen.
You won't get 100% of the weed seeds, but you'll get all of the "plant matter"