Juniper and Atlantic white cedar are the same wood, at least as referred to in eastern NC. The boatbuilders of eastern NC tend to call it juniper, and it is the traditional material for building wooden boats in coastal NC. Probably the biggest supplier is Gates Custom Milling in Gates County: Atlantic White Cedar - Gates Custom Milling. It is a huge operation. I went there a couple of years ago to purchase a bunch of juniper siding. Very nice people. They are primarily wholesalers if I am not mistaken, and I'm not sure how small a quantity they will sell. It would be worth calling them. It is not the kind of place that you can pick through lumber to find what you want. When I ordered the siding, it was ready to go when I arrived, bundled and strapped, and they loaded it on my trailer, and I was on my way.
I bought some juniper (aka Atlantic white cedar) from Jack Murdock several years ago. I've seen some references that also call juniper Eastern red cedar but what I got from Jack was definitely not Eastern red cedar.
The lumber company in Gatesville (mentioned above) is the primary source for the boat builders on the Outer Banks. I have purchased from them and also form a lumber yard close to Columbia, NC, on highway 64 not milled whose name I can't remember but I can get for you if you want non-milled. The non-milled seemed to have a lot of waste.