Some stroke patients can hold onto a ball, but not a regular sized pen. So the solution is to put a ball onto a pen. The large surface area of the ball allows for weak fingers to hold onto the pen. I used tinkercad to create a 50mm sphere with a 9mm pen hole that is offset from the sphere center. There are 2 set screw holes at 3mm each to secure the pen.

Printing on a modified XYZ DaVinci 3D printer...

Print is almost complete.

Tap for set screws to secure pen.

Ball with pen