This guy 3d prints custom handles he does a great job super easy to work with and low prices. He prints all my handles. Just let him know what you need and he will come up with something. EXCELLENT customer service. They come with a set screw. Just keep in mind the diameter of the shaft on your model chair and let him know.
INVACARE shaft size 3/16"
MOST QUICKIE, PRIDE PERMOBILE shaft size 1/4"
but double check shaft size
his shop on ETSY
https://www.etsy.com/shop/Quadclocks
his Facebook page
https://www.facebook.com/James-workshop-113605140349107