I had some minor front end damage on my coach and my local body shop was able to order the paint using the codes provided with the coach. I would imagine he had to purchase a gallon. I would think that you could reach out to any Winnebago dealer and order the touch up kit that comes with the coach which has one small jar for each color. They may sell larger containers. I've always had good luck with ordering parts from Litchsinn RV in Forest City, IA. https://www.lichtsinn.com/
If you look at the online parts Catalog the paint diagrams show a part number for each color.