Easy grip iphone 6 case for arthritic fingers

Can anyone recommend an iPhone 6 case that is light-weight, slim, and makes it easy for those with arthritic fingers to grip? Rubberized perhaps, something that doesn't slip off surfaces. I am not that concerned about dropping it but just need something that is easy to grab onto. My phone has an "Invisible Shield" so no worries with the front of it getting damaged.

Without a case this phone is impossible -- slips out of my hands constantly. An Amazon search comes up with 7 million cases for iPhone 6! No filter for "arthritis" or "disability" or "old folks!"

Thanks!