I am afraid I am only able to offer the Windows version on Steam for the time being, as uploading games to Steam is a more complex process and I do not currently have a Mac computer with which to do the required testing etc.
It might be that, when the studio is larger, that is something I can remedy but, as it stands, the Mac version is only available on itch.io
Sorry I could not be of more help and thank you for your interest.