Try Ingle Hoffer stone ground.
Best mustard I ever had came from one of those sausage and cheese samplers that you see at Christmas. It was Old Wisconsin, including the name on the mustard. Can’t buy it by itself but I came up with something close by mixing 3/4 Inglehoffer Spicy Brown with 1/4 Inglehoffer Sweet Hot.
Pricey, but good!