BUMP.
I asked for the file for the white (nylon?) stem, but it turned out to be quite easy to do in 123D Design.
Someone suggested $3 stem blanks from Vermont Freehand, but it would cost at least $6 shipping to me in Canada, plus $70 for the tenon turning tool, plus shipping for that, plus USD to CAD exchange, plus customs duties and taxes. A $3 blank is NOT an inexpensive solution!
A 3D printed pipe stem will cost me a couple of hours doing the design (which was fun anyway) and a few cents of 3D filament. The one I made is at
Thingiverse if anybody is interested. Will post photo of the prototype when it's finished printing.