Looking For A Tiny IP Cam With 50mm Lens

I would try to talk to someone from nuclearsolutions@rolls-royce.com they make custom cameras of all crazy types for extremely harsh environments.

Disclosure: I work for Point Grey.

While not strictly an IP camera, the Point Grey Blackfly is as close as you can get to a golf ball size camera (29x29x30mm).

If you can find a 50mm M12 lens, you can use a CS mount to M12 adaptor for a very small solution.

This one works too. I use it for training with 5-50 CS Tamron, double Night/Day settings profiles which is rare on the market (VVK IP8152)

Thank you all for the suggestions so far.

You've been giving me quite some food for thought here.
I especially like the M12 lens suggestion, cause as Sean already mentioned, the lens itself will already be quite big.

I'll keep this post updated on what I'm actually trying to build here.