Nothing new motorcyclist has been doing it before e-bikes. Zip tie and a piece of rubber.
That looks like it would do the job. 👍
I've also seen a version with just a zip tie. A really big zip tie with a large locking end.
I went with the Velcro thumb throttle attachment for $19 from 1859 Northwest. It comes in different colors, transferable to other twist throttles, and easy to adjust.
https://1859-northwest.myshopify.com/products/e-bike-thumb-throttle-attachment
(https://1859-northwest.myshopify.com/cdn/shop/products/throttle_red_only_900x.jpg?v=1580856294)
Couple zip ties in various locations works well. I wear riding gloves every ride so they don't need to be huge.