N.B. As you probably realise, it is usually much cheaper to book directly with the owner, if you can.
There are excellent Facebook pages, for example, where you specify what you are looking for, and owners will respond:- https://www.facebook.com/groups/bookholidaysdirect/?fref=nf
Also - https://www.facebook.com/groups/TheBookDirectMap/ with properties pin-pointed on a world map.
My email is firstname.lastname@example.org