I've personally not met a stock camera app that has png as an option. Actually the alternative camera apps I've used haven't had that option either, but of course that doesn't mean that there aren't others out there that do.
Though to be honest it seems a slightly unusual request as I've never met a dedicated camera that stores images in that format: jpg, various raw formats and sometimes tiff, but never png.
I assume that the motivation is quality, and so you don't want to just convert jpg to png (which many apps on all platforms can do).