I had a skull and antlers that I kept around and then decided years later that I wanted to have it mounted. Got some references from friends of taxidermists and made some calls to see if they had extra capes. I ended up finding a guy who charged an extra $40 for the cape. You should be able to find one.
If you live anywhere near NE Ohio, I'd be glad to give you his #.
I also like the fact that I don't have to make the decision on whether to have a deer mounted or not right away.
Keep life simple...if you hear hoofbeats, think horses, not zebras.