Piece of cake!

Grab some clear plastic from a soda bottle, etc.

Cut it to a regular shape ( think along the lines of a LOW instrument panel edge ) and glue it to the inside of the existing canopy.

Affix the broken section to the plastic.

Lightly sand the broken section to smooth out any imperfections caused by the glue.

Paint the forward edge as if it were an instrument panel, etc...

Apply some trim tape, and it will look like it was made that way.



Or.... as suggested in an RC Magazine....

Shape a block of wood, to the approximate shape of the canopy...

Get a clear plastic bottle and cut a large clear section out...

Using a covering mitt and a heat gun, heat the plastic, and press and smooth it to conform to the shape of the wooden canopy shape.

Keep working it to you obtain the shape you want, cut out any excess, and you have a new suitable canopy.