My wife and I found a quiet cottage on 4 acres of land in Oregon for our honeymoon. It was just the two of us for four days with nobody in site. The area was surrounded by a hot spring so we had a natural hot tub so hot we had to put cold water into it before entering.
Not sure what your idea of secluded is but we decided to just do a road trip for our honeymoon (we are from Vancouver, BC) and spent more money on our 1st anniversary trip when we went to Australia for a month. about 6 years ago