I was posting about MOPS. They arent gentle parenting exactly, but they are Christian and from my experience very accepting. They have speakers most weeks and you can make requests so maybe you could put in a request for someone to come and talk about gentle/attachment parenting and see what they say.
They are international so there should be a group somewhere near you if you are interested.

I dunno if that helps or not. but I am so impressed by how lovely everyone is in my group I couldnt let it go without a mention.