I have tried some popular dating sites and attempted to tell them that I'm AB/DL and so far that doesn't work. I have also tried Fetlife and other fetish friendly and AB/DL friendly dating sites and find that I just don't care much for my options usually.
I'm a bad example here, but I really feel like it will eventually come down for me, to just getting out in the real world, finding somebody that I enjoy being with, and then telling them I'm an Adult Baby before our relationship becomes too intimate. Then our relationship will either fall apart, or it will be flipping amazing, either way, I have to find somebody that will love my little side, and I just don't feel like online is the place I'm going to be able to get it to happen, at least not very soon anyway.
I think you might just have to not look for people who are AB/DL friendly, and look for people who are friendly and quite open minded. If you can find a partner who is pretty liberal, you are probably going to be good.