It sounds like the "porn-free" part isn't really the important part to you, more that they are just honest and willing to make compromises. I'm sure there are a fair amount of people who are porn-free but would be annoying to be in a relationship with anyway (thinking of some people I've seen on r/NoFap).

As to how to find a partner like that, I don't know. I guess you just put yourself out there doing the things you normally do and keep your eyes open for someone who seems like an honest person?

If that isn't the case and you are actually looking specifically for people who are porn-free regardless of anything else about them, then like you mentioned, I'm sure a Christian church would be a good place to look.