There were a number of posts on this forum a few years back about the Plymouth Brethren of which the Close Brethren group was an offshoot. See
here. You will have to scroll down a bit to get to the posts in question.
But I rather doubt whether they went in for open air preaching, although I could be wrong about this. And since they did not believe in having formal places of worship they did not have churches either.
Actually, I have been writing about them in the past tense but as a religious group they still exist, albeit not in large numbers as far as I know.