I know you didnt say shirt, but a 19th century osnaburg trade shirt should get you set up for your upper half
https://www.townsends.us/collection...s/19th-century-trade-shirt-in-osnaburg-oh-131
For the pants I suggest what appalachian hunter said.
Look for mexican war uniform trousers.
As for the coat, if your talking about his reddish wool lookin coat and not his buffalo coat, I may be able to direct you to a couple close look alikes.
Townsends has a red wool blanket shirt (coat) that has a resemblance to Johnsons coat, only difference is its not buttoned down the front.
https://www.townsends.us/collections/coats-frocks-and-jackets/products/blanket-shirt-sh-121
Now this coat is not documented easily.
Also Northwest Traders canoe jacket (might not be HC, but then again most movies are not also) is button down and looks like johnsons coat execpt it has a single cape.
https://www.nwtrader.com/capotes_styles.html
You could also make it yourself, I've never made one, but you could try wool blankets, or for a less bulky coat, you could use broadcloth.
Hope this helps you.
NWT Woodsman