Sears used to sell kit homes from their catalogue. There is (was?) a community comprised of them on Staten Island in NYC.
Nationwide Homes of Martinsville, Virginia is manufacturing small modular cottages, that can be ordered with solar already installed, pretty cool looking, they might have gone too upscale with the materials for the current market, though, fairly pricey for the square footage. Eco-Cottages, online PDFs on their site.
Montgomery Wards also sold kit homes.
Sears would deliver them via train car back in the 20’s. Very common in Iowa.