I restored mine, but I would say buy new. Your boxes are true rectangles so it should be easy to find something slightly bigger to replace them. Cut the openings bigger to accomodate, and replace the trim.
You can avoid having to cut the gunnel openings and replace trim by restoring your old boxes. You can use some type of plastic weld behind the edges of the outer flanges. Then putty, sand, & spray paint the inside. Just a light sand and oil or finish for the teak.
Edit: Just saw how badly yours were broken in your pictures. Buy new, for sure. Or maybe you could build some out of 1/4 inch starboard.