What the title should have read is how to find another cottage in Wales when Morawel is booked up. Because reading this you have already found the best cottage.
Google maps seems like the best choice to me. Go to their home page and select maps and type in something like ‘Holiday cottage Wales’. Then zoom in or out on the map to find the location you are interested in.
You are probably going to find cottages advertised by agencies or by individual owners. Some websites reflect that and perhaps location, size and price might be a better indicator than a slick website. Although booking thru an agency you should get a reasonably good professional services.
There are a number of excellent sites for browsing cottages, so good luck in finding the the second best place to stay in Wales.