I am searching, image by image, the 1793 baptisms in "Bautismos de hijos legitimos 1792-1796" (as FamilySearch has labeled it) collection for a natural birth, since there are no other baptism volumes for this period. And the volume does indeed include hijos naturales (almost always with simply the abbreviation h.N. or h. n.). So if you are looking for an hijo natural in Nochistlan do look in the baptisms, since they do include hijos naturales even though they are titled by FamilySearch as hijos legitimos.

Here is the URL for image 71 of 308 which is in the 1793 baptisms (just a randomly chosen image so you can see the records - the one at top right is "h. N."):
    familysearch.org/ark:/61903/3:1:939N-GYV3-V?cc=1804458&wc=3P9Z-FM3
FYI ... I am looking for the baptism of Feliciano SANDOVAL h. n. de Maria Lugarda SANDOVAL, according to his 1814 marriage to Maria Marsela CAMPA that shows him age 21, originario de Rio Ancho.

    Wesley Johnston