Cleaning up in the garage...

[luvmysuper]

I don't think you'll find a similar type donor handle for a larger knot. That Craftsman screwdriver (I have an awl version) you used is probably the largest (width) of the handles they have. Unless they have some industrial sized tools ($$) that aren't in the mainstream market. That brush is simply phenomenal. A true working man's brush!

I have an old "Professional" model that has a considerably thicker handle, it is also considerably longer.
I may take that one which is badly scarred and see if I can shorten the handle to a reasonable length with the widest portion to use as a handle base.
The advantage to that is there would be no through hole left over from where the driver bit was removed.
This is the type I mean

 

[Hercule]

Good luck! I'm sure we'll all be interested to see what you come up with. Those stubby handles are great because they're just the right size (if a bit narrow) for a brush. The best part is that they are so obvious about what they were.

 

[luvmysuper]

Good luck! I'm sure we'll all be interested to see what you come up with. Those stubby handles are great because they're just the right size (if a bit narrow) for a brush. The best part is that they are so obvious about what they were.

That's a very good point.
This latest one I modified looks ok, but it certainly isn't clear that it is a Craftsman screwdriver.
But I'm a softie for Lucite type handles.

 

[Hercule]

Reminiscent of some of the Omegas I've seen. Interesting, upside down like that. I've long thought that shaving brushes seemed backward in that way. But, I've been accustomed to it.