Rabbi Avinoam responded:

Here are some sources in my Shomer Emunim on free choice. If you want to see the original Hebrew for any of them, I have them to hand but can only give them to you tomorrow or maybe even next week. I have a major work presentation today. It might be helpful to look around at the context of some of the following sources in my book.

The main source relevant to your question is probably: pp.709-711, fn. 261

Other sources that may be of interest:

p. 321, fn. 9

pp. 686-7, fn. 211

p. 882, fn. 503

p. 892, fn. 517

p. 895, fn. 521

Hope this is meaningful.