Your best options are to attend local munches, to find fellow kink folk, and to be open on your dating profile. I found putting "Kink friendly" helpful in weeding out people who were not kink friendly. Finding someone with a niche fetish is going to be difficult, but finding people open to kink in general is much easier. Just be honest, open, and adventurous and you'll be fine.
I've used Grindr and GROWLr and a few other apps for over 10 years to find local interest. I use a messy photo and talk about it in the bio. There have been a few into it but mostly you'll get people curious and wanting to try.
There is also 'Recon' full range of fetishes on there app and website.
Personally i prefer UMD, don't forget you can kinda search by location on here (if there is a location recorded on the profile), by putting your location/region into a 'people' search.
I find honesty on non-kink apps (okcupid, tinder) got some interest. Fetlife seems dead for WAM but good for meetups for munches and thus other kinksters. There isn't a wam/kink specific app, there are some advertised but they are fakes for cash and data mining.
Also this isn't a millennial thing, im gen-x and happily use dating apps.