I sympathise, but...why do we need a niche? The term is used excessively by marketers nowadays, and implies that you want to find the pool to be a big/small/medium size fish in. And then you can be labelled so people can find you easily on the racks.
But most of us (even professionals, like Harvey and others, I suspect) are in it primarily because we enjoy what we do.
So - enjoy what you do; find those that you enjoy listening to, and play them your stuff; the chances are they will appreciate at least some of it.
What niche is Tom Paxton in? Or Ralph McTell? Or Eric Bogle? Or Andy Irvine? Or...etc etc. Pick the "big names" you like - that's your niche.
But I repeat: you don't need one. Don't look for labels. Look for people, individuals who like what you do.