I think INFJ's can be found many places. Best bet, I tend to think, is to pursue some sort of activity you're really interested in. There's quite possibly an INFJ interested in the same thing.
But...common interests tend to be where you meet like-minded people anyway.
The only reason I'm not throwing out specific things is because I know 3 other female INFJ's in real life, and we're all into very different things. One is super-busy and historically did endurance running/triathlon stuff as her main hobby, but has also done horse-riding with handicaps but is mostly too busy with her job, another isn't really involved in anything and I'm not sure where you'd meet her outside of online forums, a third is very into her religion and volunteering and you'd find her at a church, and as for myself.... if you'd find me anywhere outside of my own house, the coffee shop on occasion, or this library where I do internet these days, you'd find me hiking, at a climbing gym, or on an irritating online dating site.
There's no one place, sorry to burst your bubble. We come in many different flavors.
"...On and on and on and on he strode, far out over the sands, singing wildly to the sea, crying to greet the advent of the life that had cried to him." - James Joyce