Were can i buy original camera in iphone 12?

I'm not sure. Apple has a self-service repair page that mentions the ability to buy genuine parts, for some products, at a Self Service Repair Store. But there are only a few entries in the Country/Region pull-down menu.

Self Service Repair - Apple Support

Oh wow… thanks for the correction. They’ve added parts since the last time I checked.

Consiering the fact that it is not at all cost effective to go the self repair route, I don’t look at it that often.

See if there's information here: Self Service Repair - Apple Support

It looks like you can. The parts shown available for the iPhone 12 are battery, bottom speaker, camera, display, SIM tray, taptic engine, and TrueDepth camera.

You can’t. The only parts available from Apple for self repair are the display and the battery.

You're welcome. Yes you're correct, when they first came out with self repair, it was only the battery and screen available I believe.