The convention that I follow is that leather in brown or black, with or without a brass or silver cantle, is appropriate for daywear and that fur or hair with a metal cantle is appropriate for eveningwear (full-mask sporrans being the exception as they're fine for both day- and eveningwear).

These "Semi-dress" sporrans, in my opinion, come out looking like cheap attempts to make a fur sporran and I wouldn't wear one.

If you want a fancier sporran for day wear, a black or brown leather "hunting" sporran with a metal cantle looks quite nice.