Are you willing to commission something? I've got some guro works here: https://archiveofourown.org/users/whydoihavethiskink/works
I don't have any works with f-on-m snuff (people haven't requested it yet), but it's a perspective I can write. My commission rates are $20/1000 words, usually minimum 2000 words (it's usually difficult to fill a typical client prompt in enough detail otherwise; 2000 words is a pretty average short story). Email me at firstname.lastname@example.org for more details!