I've been thinking about trying to build a Nernst lamp for some time, but I have no idea where to find a suitable source for the glower.

The Nernst lamp was actually quite good, it used about 60% of the energy needed for the early carbon filament lamps of similar wattage, and could last a good 700+ hours of burn time (which is not that far off from cheap incandescent lamps now, which last around 1000 Hrs). There were plenty of claims about "better lighting quality" over carbon lamps, but I suspect that marketing blurb, same as the lamp manufactures spout even now...

(though it may have been true about arc lamps, which were also in common use and had harsh glare and flickered.)
One thought that crossed my mind was to try and adapt a Silicon carbide "Globar", which is somewhat similar to a Nernst glower. The SiC globar is electrically conductive at room temp, unlike the Nernst glower, so no need for the heater elements. But I have no idea about what sort of light output (if any) is available from a globar as they are primarily used for IR heating and near-IR light sources. Maybe it's possible to coat the globar with Yttria-stabilized zirconia, which would solve a few issues with building a working lamp... But I have a feeling that this will require either Sputter deposition or Plasma-enhanced chemical vapor deposition - neither of which are likely for any of us to do at home.

Unless it could just be pasted on and dried? Maybe some sort of paint or cement like paste??
SS