Have you looked at The Wargame Vault http://www.wargamevault.com ? There are all sorts of things there including card models and 3D printing files for buildings and terrain in different scales.

For example here is a modular gun emplacement. It is for 28mm models but it suggests that it can be rescaled.

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It may be found at https://www.wargamevault.com/product...rs=0_0_40212_0