Sony has made a cute trio of compact lenses that are thought to fit perfectly for your A7c camera. Here is the only review you have to watch to know everything about this lens:
Preorders:
24mm f/2.8 at BHphoto. Adorama. Fotokoch DE. Park UK.
40mm f/2.5 at BHphoto. Adorama. Fotokoch DE. Park UK.
50mm f/2.5 at BHphoto. Adorama. Fotokoch DE. Park UK.