Openly, honestly nowhere. The bodybuilding, muscle, weightlifting community is very homophobic, (which is funny that I can probably name hundreds of household weightlifters that have modeled for Chaosmen, Randy Blue, Men.com etc.) and you think guys who become swole like that would mind the attention/agenda of other guys, but I noticed some of the most homophobic/asshole guys out there, are the muscle/weightlifting/fitness guys. It's something I don't get, but yeah.
It would help if you're muscular/bodybuilder yourself, and I argue it's kinda something to where you're gonna have a very difficult time if you're not. These guys eat, bring, drink gym and weights, and I assume they wan't their partner (whether openly/or more discreetly) the same as well. I'm not saying there aren't some muscle and big powerlifter guys who are looking for a Peter Pan Twink sissy. I know they exist, as I've seen them out there lol. However, these are exceptions not playing by the rules here.
But if you don't mind some DL guys in the muscle community, they are out there. I don't know how gym rules or the gym culture works, but I've noticed a lot of guys don't like going to the gym alone, so you could end up being a gym buddy/spotter and vice versa for him, and who knows, things might expand more than that.
If not you can check out bear bars, usually they have some guys in the bodybuilding community that go to those, but yeah.