We will be using this current product as inspiration for some design factors such as conforming the insert well to the face, including the nose in the insert, and keeping the insert positioned correctly in the mask. This specific product was rated quite well for these considerations, so it seems worth it to study before initial prototyping.

https://www.amazon.com/Silicone-Homemade-Comfortable-Breathing-Washable/dp/B08931ZQZC/ref=asc_df_B08931ZQZC/?tag=hyprod-20&linkCode=df0&hvadid=475746763412&hvpos=&hvnetw=g&hvrand=6951272405986858367&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=1018405&hvtargid=pla-952239952316&psc=1