I saw some nice kits and structure detail parts for scratchbuilders being offered by Rail-Scale-Models [ https://www.rail-scale-models.com ] at a train show in western North Carolina last weekend. Their line includes items for N, TT, OO, HO, S, O, 1:35 and G Scales, so has something for everyone.
I asked the Owner about Z Scale items and he said that if someone has a specific need, he might be able to produce it.
They do. I seem to recall a thread here some time ago where many of us were lamenting the loss of familiar names in structure detail parts. It's great to see someone stepping in to fill the void. I can't wait until my N Scale layout progresses to the point where I can begin to think about structures. I scratchbuilt numerous buildings on my last layout because nobody produced what I had in mind.