Some general BDSM fiction sites have F/m stories; the trick is to locate them.
BDSM Library has a search box, searching for dominatrix in title or Femdom in synopsis locates several F/m stories. Other keywords may work as well.
Here’s the opening sentence from a story chosen at random:
The crack of the sleek riding crop blistered the silent darkness and echoed off the concrete walls as it hammered another violent battery on the hard, throbbing penis that was its target.
Wayne C. Rogers specializes in Stories of cuckoldry - not a part of my fantasy life - but maybe yours:
Taking a deep swallow, I stepped carefully off the stool and felt my arms stretch upward to the ceiling. Sandra pulled the stool away from me and said, “That’s just the way I want you.” I was pressed into the corner of the room, standing on the balls of my feet to help ease the pain in my wrists. “This isn’t comfortable,” I whined. “It’s not supposed to be,” she stated. “In fact, my wrists are starting to hurt really bad,” I said. “Then, you’ll just have to raise up higher on your feet to keep the handcuffs from cutting into your wrists,” Sandra said as if she didn’t have a care in the world.