I think it’s admirable that you want to help your friend out. That’s how good friends feel.
With that said, I have to agree with the others that taking your friend to a gay bar to potentially hit on participants of a bachelorette party will unlikely bring results. When I go out with the girls, and if we were to choose a gay bar, that’s sending a pretty strong signal we they don’t want to be hit on by men.
It’s difficult, if not impossible, to convince a person to ‘calm down’ and that when the time is right, they will find the ideal partner. While it’s often the case, there isn’t any guarantee that this will be the fate of everyone.
A better strategy for your friend is what @chyna suggests: he needs to get out and join business groups or clubs that hold personal interest. Dating sites shouldn’t be ruled out either. As @Trillian points out, members have to weed through a lot of profiles to find potential partners, but it’s much more interesting than the bar scene (IMO), and there is a certain degree of assurance that they are single as well. More of my friends are finding their partners through online dating sites, and they are all professionals.
A better way to help him cope with the disappointment (or depression, as you call it), would be for him to talk to people who have found the right partner at 30 or over. They are more likely the ones who can paint the picture that at the mere age of 30, it isn’t time to worry about it.
I wouldn’t mention that he’s being too ‘picky’ either. There’s nothing wrong with being selective. If more people were, there might be less divorces in the world. One of my best friends from school married because, according to him, “She was the first woman who would sleep with me.” Not surprisingly, it didn’t last. That’s an extreme example, but it makes a point about lowering one’s standards.
Please keep us updated, if possible. It has the makings for a good romance story.
Edit: One more thought based upon personal experience. It’s much better to focus on living a single life with the expectation of never finding a partner. A roommate at one point was dead set on finding a husband, and she was miserable. I just went with the flow. It wasn’t until I was in my mid-forties before I met a person that not only met but exceeded my expectations for the ideal mate. He was more like your friend, according to your mother. Yet we both know now that it was worth the wait.