Forget the white fur sporran if the money can be spent on something you really want. I don't know what black leather sporran you are lookihg at but there are plenty that would be more than acceptable for formal wear. Have a look on some of the merchants sites thru google. I am sure that I have seen pics of grooms wearing PC's with black leather sporrans(sorry can'rt remeber which sites)

I know you want everything perfect for the big day, and so it should be, but be aware, the lovely bride will get most of the attention and what you are wearing will never get as many comments as the bridal gown.
All the best for the big day and believe me, it will go so fast