Thanks everyone for the input. I'm glad to see that everyone who responded thinks you can have a formal sporran without using the fur. I've seen quite a few options online that I think look VERY formal without using fur.

To me, workmanship is the real factor in whether an item is formal or not. If someone goes out of their way to make a product that looks classy and portrays the attitude of "yes, I am going to some extra effort to look nice for this event," then that's a formal item.

I just wanted to see how everyone else felt about that as I don't want to be insulting to a potential event host by wearing something that is not considered proper, particularly in the realm of a style of dress I care about.