Cheaper to go to ebay and look up sporting goods and type in crow decoys and find they are not that expensive at all. The other is to buy a hawk or owl decoy and once you shoot a crow lay it somewhere beneath the owl or hawk and you will have the mother natures' answer to your lack of decoys dilemma!
But if you do; first get rid of that shine on the hawk or owl by buying some dull-cote and spraying the decoys "dull" or acceptable. Or else hunt only on overcast days? Dull cote or similiar is a clear dull coat paint you can get at your local hardware store or hobby shop or wal_mart.