I've put the "White Spot" on black replacement stems by drilling a hole the proper diameter of the "Spot" in the right place and filling it with white epoxy. Just make sure to not drill into the bore of the stem, just drill deep enough to give the epoxy some purchase. Fill with epoxy and let it stand a little proud of the stems surface. When it cures a light touch with some fine grit paper to take off any excess, buff and wax and you're good to go.
Dunhill replacement stems used to be made by a man in NJ, not sure if they still do that anymore but AFAIK they don't go back to England.
BTW, jchaplick, I see in the post of your pipe for sale back in 2008 that it's stamped C137. I believe the "C" means it was a Churchwarden and the bowl looks very much like a Dunhill Churchwarden I have. The length of the shank and the cant of the bowl are very similar to my pipe on the left in the photo below.
If you do decide to have it restemmed as a churchwarden be warned. The Tanshell second from the left in the photo
also had a "C" and came with a short stem. I think it means it came with both short and Churchwarden stems. Anyway, I sent it to Dunhill to have it restemmed and the Churchwarden stem it came back with was way too thick and clunky, it had no grace at all. I had to have it reshaped by another pipe maker to get it right and you can see it still looks a bit thicker than the others.