I have had a lot of people contacting me about fixing webcam and microphones of very old and/or dead laptop and PCs.
When the answer turns into "buy a webcam" that too becomes a problem.
Webcams are sold out all over the place for obvious reasons, so if you are desperate perhaps this article here will help you i.e. use your smartphone as your webcam.
A couple of things to point out though:
1) It isn't as straightforward as it may sound but the article does contain all the help you should need.
2) The article ONLY talks about using your iPhone, HOWEVER, many of these app's are also available in the Android world.
3) And, as the article points out, you are better of use the dedicated app' for the applicable video service on your smartphone that trying to link together a hodge-podge of devices.
But, as I said, if you really need to, you can :-)
DISCLAIMER: I haven't done this and I don't plan to. See point 3 above.