Most of the Vivec City traders (PC/NA) have relatively inexpensive (< than 10k) white pieces with nirnhoned trait. Varies of course, but that's where I buy them. Usually Lorthodaer and the orc whatever his name is have the best selection.
Would help if you mentioned whether you are on console, or PC NA or PC EU, seeing as your question is about specific traders. But just jump around. Busiest traders have most often, so if PC NA go to rawlkha, then grathwood or mournhold, then Wayrest, then Alinor if you got Summerset, Vivec if you got Morrowind, then from there take your pick on any of remaining less popular locations with 5 traders (Daggerfall, Sentinel, Shornhelm, Riften, Stormhold etc etc)
I don't bother with TTC for white nirnhoned pieces. Vivec's good enough. WAY too much effort to look it up on TTC, sort by price, then deal with multiple loading screens just to find out they're not there anyway.
Of course, I'm not worried about anything up to 20k in price anyway.
It took me searching through a few before I finally found a dagger that had Nirnhoned on it. So, to answer your question, yes there are some guilds that offer it. Just have to spend time searching.
I am patient with stupidity but not with those who are proud of it.