I have the same boat with the wood side strips above the windows. At the boat show they looked just wonderful, but over time they dry out, split, break at the screw install point and start looking horrible!! Mine were varnished by the previous owner long ago and were tough to refinish. I do not know if they are available or even how they could be shipped, but if you find anything out regarding availability from the factory, please post!
Only options are to remove, fill in the screw holes, compound and wax, paint a strip or fabricate a new one. I do not think that removing would change the look of the boat given that the window design on the Mark II provides a nice linear look. I am opting for removing, filling in screw holes (small), compounding and waxing.
Bob
1988 Mark II