The smaller the camera (and cheaper) the more issues you're going to have. Especially if you're looking at cheap chinese spy cams or something. No one makes a specific camera for "model trains suspended from a ceiling", so the closest you'll have is an action camera that's probably waterproof... so you'll always have features that you don't need but are paying for.

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You could try these other camera's, not cheap, but may be a better size

Kodak PIXPRO SP360

https://www.amazon.com/Kodak-SP360-Explorer-Accessory-Pack/dp/B00NFTHQW8/ref=sr_1_3?crid=3BFORX1CY2DV2&keywords=kodak%2Baction%2Bcamera&qid=1679679057&sprefix=kodak%2Baction%2Bcamera%2Caps%2C172&sr=8-3&th=1

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RunCam 5 4K FPV Camera 1080P

https://www.amazon.com/RunCam-4K-Xview-Sport-Camera/dp/B07SMNRLBG/ref=sr_1_9?crid=3BFORX1CY2DV2&keywords=kodak+action+camera&qid=1679679057&sprefix=kodak+action+camera%2Caps%2C172&sr=8-9&ufe=app_do%3Aamzn1.fos.f5122f16-c3e8-4386-bf32-63e904010ad0