D2 compatible parts seem to pile up in drifts, I've discovered since acquiring a D-II. D2 parts are interchangeable with the D-II in general, and many are interchangeable with other models. You need the 2-1/2" cone for 135mm. The flat board is for lenses up to 105mm, and the 4-1/2" cone is for 150mm.
Lensboards, negative carriers, and oddball accessories are very easily located. The bulb is an ordinary enlarger bulb (211 if I remember correctly--it says on the plate on the head). My favorite negative carriers are the glass Rapid Shift carriers.