Where'd the Google camera app go?

As @beeshyams said in their comment, the Google Camera app is not available in some regions on the Play Store. This link is to the listing on the Play Store. If you can access the listing from that link, then you're one of the lucky few countries that can. If you cannot, you will have to download it from a reputable third party website such as APKMirror.

Do take note of the minimum supported Android version when using APKMirror as well as the fact that there are two variants for different processor architectures. If the minimum version is too high, I recommend moving to the most recent one that supports your OS version. If there are two variants available for whichever version you choose and if your first download doesn't install, try the other variant.

DISCLAIMER: You will have to enable Installation from Unknown Sources in order to install from a third party site. This is highly recommended against as it enables the possibility of malicious applications being installed on your device.