Lion Country Supply has them for sale. Here's a link
http://www.lcsupply.com/store/flashcart.cfm?section=510But if you want to make one like I did, it should have a 6" opening on the outside and funnel up to about 4".
The center of the outside opening should be about 6" off the ground.
You want it angled up so when they go though, back into the pen they have to jump down. In other words the opening on the inside of the pen should be above quail eye level.
Hope you understand how I'm explaining it . Let me know if you need me to explain some more.