Well its regular wipers I assume

the tiny pic will do.
You could also try a dremel and a milling bit. If owned. Cutting it in half will destabilize it a bit. No idea what kind of
wood you got there, but some are quite brittle. Carving in a bed for them, in an accurate way (they should stay out same angle right?)
would actually be more difficult imo. If you have a saw....sandwhich it. Cut out the core piece with the empty spaces for the wipers,
then screw on 2 grip shells. Know what I mean?