All this chatter about 10-10's reminds me, I am now making the handle inserts on my 3D printer.
Here are examples of the older rubber insert, the hard plastic insert, and the 3D printed insert. Due to the way the 3D printer works, the handle has a sort of wood grain look/texture. It is just a little bit larger than the original hard plastic version.
I have not had a lot of success installing the rubber ones as they are a really tight fit. They are also a bit short.
The hard plastic ones install easily and are held in place by the screw that holds the lower brace to the rear handle. They don't really fill all the space in the rear handle but do make it much more comfortable to hold on to.
The 3D printed one fits snuggly in the handle and are also held in place by the screw that secures the lower brace to the rear handle.
I have not been able to find the hard plastic ones (89320) from any of the usual sources so I have installed these in several saws that were missing the insert. I do have some available, if anyone is interested send me a PM.
Mark