Honestly, good luck. I suspect there a few out there, but due to health regulations and cops coming down on sex traffic from time to time, they are a rarity compared to the wild and woolly 70's.
This is one of those areas where the fantasy is better than the reality. I have seen many a setup pro pic purporting to be a "gloryhole." Amazingly, there is never a telling of WHERE it was. . . sure, it was in a constructed studio! If you look on craigslist, you can find a few guys who have their own private glory hole set up in their living rooms and take "all cummers" some nights. But think about the reality. . .
Maybe at a party night at a swingers club. . .