I have a second hand Taka Appalachian dulcimer. Not a high quality instrument, but I enjoy playing it. When the brittle, old plastic bridge snapped at the low string groove, I decided to try replacing both the nut and bridge myself. The micarta but and bridge looked to be sturdy, inexpensive pieces.
This was the first time I'd done this type of repair, but the micarta material is easy to work with. Miter saw, file and sandpaper, and a small mallet were the only tools.
These pieces were wider than my plastic ones. I think sanding the sides to make them thinner would work fine, but I didn't try this. I widened the nut groove because all of the frets were a bit sharp (cheap instrument).
I think the stronger nut and bridge have improved the sound, and I have enough material to replace both nut and bridge again should something happen.