Generative fill for missing pattern

Nicole, I stumbled through, trying different tools to select the white ovals (white in the pattern stymied that).

One way that worked was too complicated for me to 1. try 2. repeat to record due to my deficiencies; I tried creating two oval selections with the elliptical marquee tool, then generate the fill. There had to be an easier way. 

My next pass was just making two rectangles with the rectangular marquee tool set to 'add to selection,' then running Edit>generative fill. See the movie.

Just download original vector image from freepik.com, rotate 90 degrees, and combine more of them to create bigger background, no AI needed:

https://www.freepik.com/free-vector/twigs-hop-seamless-pattern-with-repeating-images-malt-leaves-hand-drawing-white_11243902.htm

OK, not exactly your pattern, but definitely from same author, you can search more on freepik, if not good enaugh.