Have had my 2016 C Two for less than a week and I commute 75 mi each way. I'm getting pain between my shoulder blades and in my neck. I was going to purchase a memory foam cushion and neck pillow from Amazon but thought I would check and see if anyone had one to recommend. There are a lot of choices available.
Here is the what I have and they are great Love Home Premium Memory Foam Car Lumbar Pillow & Car Neck Pillow Kit (Grey) from amazon
What I did was buy some foam cushion and hog rings from amazon. I made a pillow that was 10 inches tall by 8 wide and make sure that the middle is 2x as thick as the ends. How thick is your preference. Push the foam under your seat covers and it will look stock and feel great too.
My biggest disappointment with the car - which I love otherwise - is the poor ergonomics. The steering wheel has too little adjustment fore and aft. If only the seat went back another inch or two! I suffer badly from sciatica, my smaller and older little Daihatsu Charade had much more comfortable seats, and better leg room, both in front and in back!