The advantage of a factory pipe is that a stock stem is a possibility. It could have a slight misfit, but could slide right in place and be the perfect size. I'd give all the information possible, everything on the stamp, when and where you bought it, style name and shape number, finish, and style of stem, so you minimize the chance of a near miss. Smokingpipes, Iwan Ries, or one of our other larger online retail sponsors could probably help you, but I'd phone rather than email and work with someone who gives their name. If it comes to that, there are pipe repairmen who work more quickly than others, and if you need one, ask around. Forums members can supply many.