You can read the full paper  (Nicole Gallup, Jennifer K. Bow, and Joshua M. Pearce. Economic Potential for Distributed Manufacturing of Adaptive Aids for Arthritis Patients in the U.S. Geriatrics 2018, 3(4), 89; https://www.mdpi.com/2308-3417/3/4/89)​ and download all models here.

There is a TON of literature available on 3D printing assistive & adaptive technology, within OT and also other disciplines, such as PT, medical engineering, etc. Check PubMed or Google Scholar to find a wide range of relevant literature. 

When searching for information about creating adaptive technology, or looking for examples of 3D printed objects, you will want to be creative with your search terms. Of course searching for variations on 'adaptive' or 'assistive' will be helpful, but you may also consider including the name of the condition that may be impacting mobility (e.g 'arthritis') or the name of the aid (e.g 'button hook' or 'handle').