Hard to tell without seeing a comparison with the original brushed. The would need to fit snuggly but freely so the spring can push them into the commuter, (shiny copper section) as the wear down.
If the are too thick you will have to wear them down on sandpaper, if the are too thin you will have to build them up somehow? The ends of the brushes that contact the commuter would need to be rounded in a similar fashion to the original brushes. The length of the brushes should be short enough to accommodate the spring and allow you to close the compartment that the fit in.
The will be noisy for a while until the bed in and wear down to the shape of the commuter, run them on low speed only for a while.
Full marks for initiative.
PS hope it works, you have nothing to loose… I think.