A great place to find rough is at the annual Tucson gem show around the end of January each year. There are more shows going on at the same time in Tucson than the average person would have time to attend! If you do get to Tucson for their big show, I would also recommend you attend the Tucson Faceting club (sorry I’m not sure of their official name) as they often have some events at this time. Great time/place to meet other factors and really nice people.
At the Tucson show, all types and qualities of rough are available. Natural, synthetic and lab created rough can be found. A lot of the dealers mentioned here, can be found in Tucson, so you can meet them in person. As an example, I picked up a large piece of lab created emerald rough (a lifetime supply for me) from Chatham at the last show. They don’t sell rough online. Yes, I have heard that Chatham will not be selling rough in the future in Tucson.