What will likely happen in your situation is that you will just have an additional source of sound (second microphone) routing to one mono input channel (your camera). Hope this made sense. Take care and stay safe

If the female input on your camera is mono. The result of adding multiple microphone won't change. It will stay mono. If you have two female inputs(jacks or xlrs) on your camera And both are mono you can then pan them left and right respectively and obtain true stereo.

If the camera has a stereo female input, (I highly doubt that), then you will need a male stereo jack microphone in order to achieve what you desire. Haven't seen or heard of any on the market