BriarBlues is selling a number of Dunhills with replacement stems right now. If you don't care about originality you can smoke a clean and pretty Dunhill for a nice price.
I got a 5109 from Mike from the same lot of Dunhill Canadians - Mine had an original stem but toothmarks repair on it . For the price I could not pass it up . Smokes great.
Here is the 1984 version of the 5109 with the tapered stem. You may be better off leaving the one you have as the Dunhill stems need maintenance. I have some oxidation starting where the stem meets the shank that I have to address.