Wheelchairs or other mobility devices are not known for fully accommodating all of their users. Many customization have been made for cup holders for example like these ones. Most cup holders that exist require the user to pick up their cup to drink from it.
This client would greatly benefit from having a drink he can always access independently. He would need something to hold a cup to the side of his wheelchair within reach so he can drink from the straw.

Your task is to design a device that will securely hold a cup mounted on a wheelchair. It must not be knocked off with sudden movements or bumps in the road. It must be waterproof and very rugged. If it is made of multiple parts, each one must be easy to replace and be assembled. It should not be too wide so that the wheelchair can still go through doors with ease. It should ideally have a gimbal feature to reduce spilling.