I'd say that your query might get better responses in the Hobby forum, but the model train hobby seems to be dying out.
Look for hobby stores. They will stock items that your boyfriend seeks, including kits and prefabs for model houses.
I once (35 years ago) built an 8 foot by 8 foot train set display, including two separate track circuts, a small village for the trains to loop around, complete with tracks, tunnels, buildings, roads, street signs, grass, trees, and bushes; most of the items were bought from hobby stores. The display was used by a medical staffing company, which rented booths at several medical conventions a year and used the display as an attention-getter.
Your boyfriend can probably build the same sort of setup, except on a smaller scale, probably using
N Scale or
HO Scale components.
EDIT: Amazon has an entire section for model trains in its Toys & Games / Hobbies section.