there are lots of options...
MotherEarth News had one that uses a 5 gallon bucket that you modify
I've seen others recently on chicken sites...can't remember which ones specifically. Basically it looks like a large tube that sits a little bit above a tray. often times, you can hang them. Like a gravity feeder? I'll look for the sites , but some hold large amounts of feed.
Also seem to remember someone on BYC that made one out of PVC pipe that they could load from outside the coop area and it fed through into the coop so the chickens could eat free will.
We also have a big metal feeder; I think it holds 20 pounds. What is the difference if it sits in a bin waiting to be fed or if it sits in a feeder waiting to be eaten? The only condition would be don't get a feeder so large that the feed is in it more than a couple weeks.