Navwar sells 1/3000 harbor pieces.
Brigade Models sells 1/1000 scale terrain, lots of it. Works brilliantly for 1/1200 shore terrain.
Irregular Miniatures sells 2mm terrain. I find some of these work better at 1/2400, some at 1/1200, and a few at either scale.
Navy Models and Books has the old Triton 1/1250 harbor bits and Thetis 1/3000 harbor bits.
WTJ makes shore batteries in any scale from 1/3000 on up for the pre-dreadnought period and WWI.
Links to all of the above are in my naval miniatures shopping database. Filter for the Category "terrain".
You can also look for the Fujima 1/3000 WWII harbor kits on eBay: auction
Spithead miniatures has produced quite a few 1/1200 ACW buildings and forts, but these can only be ordered by joining a list of potential customers and waiting until there is enough demand to produce a set. The website shut down years ago and there is only a Facebook page now, but you can contact Phil Ireson (the owner) by email: vanilla55@sky.com
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To populate an entire seaside town in 1/1200, I would go with Brigade Models and never look back.
To do it in 1/2400 would require a lot of scratchbuilding. Most of the building bits in smaller scales are harbors only, not neighborhoods or industrial districts.
