.... I'm interested in doing some pieces with niello but I'm
not set up to make it right now.
Chris, if you're interested in ordering Niello from abroad I've seen
it listed in the Karl Fischer (Germany, www.fischer-pforzheim.de)
catalog (2003, p.201). They list is as "Tula", presumably the German
word for Niello, it comes finely powdered, runs 6 euros for 10 grams
or 50 euros for 100 grams, product number 7625.
I have no experience with this particular product though I've been
very impressed with the other things I've ordered from them. They
ship quite promptly and generally offer very high quality stuff.
Usual disclaimer: no affiliation with them, just a happy customer.