I am in some Meetup.com groups locally. I would not in a million years think of there being any kind of sexual/erotic meetup group because Meetup.com is not an adult/sex site. I am in soccer watching, wine lovers, alternative movies/foreign film groups, to name a few. You are barking up the wrong tree, except for having a the chance to meet everyday, vanilla women, who are at the meetups to enjoy activities related to their own interests. That said---every meetup group I have been to in my own town is FULL of women, normally the ration is like 80% women to 20% men, with the exception being sports related groups.
May I make a suggestion? Fetlife has a Tantric Sex group. I am a member in that group, among other groups. I have learned a lot by reading the threads in their forum and continue to use FL primarily as an educational tool. However, there are several groups that have "classifieds" sections where you can advertise for whatever you are seeking--including sex and/or hooking up. It is a free site but you cannot see the videos unless you "donate" to the site. One of my favorite groups on FL that I am a member of is "Women who love Cock" and many members of that group happen to also be LPSG members as well. I am also in Big White Cock, and other groups that are hung-cock related, haha. I am also in some of the Cougar groups, since I prefer younger, hung studs.
FL is a site full of very open, experimental and often kinky people. Like the title says, many with specific fetishes or sexual interests. Of course, it is also the primary BDSM site that I know of in the US. But not everyone on there is into BDSM---there is a little something there for everyone. Want to have an ANR with someone (Adult Nursing Relationship), find someone to spank you, piss on you, dominate you, worship you, lick your feet, stomp on your dick, become your domestic servant, dress you up in lingerie, rim your ass, tie you up, put you into chastity, fuck your gf/wife, suck on your toes, eat your cum, whatever.....you will find a group there catering to your kink. I just joined the Cream Pie Eaters group a few days ago---because I have never had that done to me and I want to learn more about it. I want to read about it, fantasize about it and get turned on by it. FL has a little bit of everything. Good luck.