If you have a favourite SW that you "click" with, and see with some regularity, ask them a), if they might be interested, and b), do they know anyone to fill the second "M" role?
I've had some very memorable, "bucket list" adventures under that scenario...having already established a good rapport with the "F", gives you the best chance at finding a third that "fits" well and thereby a good time for all involved...although I guess that might be true of a "couple" as well. Whenever I've seen couples advertise, looking for a 3rd, I usually get the impression they're experimenting with something new...which seems to me, has more potential to fail, & not live up to one's expectations...my two cents...🤷♂️