I didn’t know how dedicated to the process you might be.
It’s possible to leach your own lye from hardwood ashes, and fireplaces are plentiful.
The fatty acids could be leftover cooking products. But, acquired this way, the pH of such products might be hard to determine.
That bit about the rubber gloves when you wash your hands, was originally supposed to be a joke.
Everyone knows rubber gloves wouldn’t hold up long using lye soap.
*Snort* Just don’t give up, do ya.