I made my crop bra from an athletic sock (a big one) for my silkie. It was a piece of cake. I cut out the heel and measured about 2 inches and cut the sock off back from the cut heel. Put the sock over my hen's head, pull wings out through hole in the heel.
I then carefully cut extra sock material away and folded it in half to make a push up crop bra.
I have been battling the sour crop (pendulous crop) for 7 weeks: antibiotics, monistat, fast ing diet for 3 days, 3 days of yogurt, and then 3 days of scrambled eggs (crop reset diet, which was helpful), but this crop bra was my solution.
I'm on day #7 and crop is normal. After 7 weeks of battling this issue (and feeling rather hopeless), she's laying eggs again after seven weeks of not. And not head bobbing and uncomfortable.
The nutrition is getting down into her gizzard again and not fermenting.