Replacing the entire seat could be less expensive than having cushions made. There some issues though.
Off the shelf seats with cushions will probably be white, not the Grady off white. Maybe that isn't an issue.
Those seat sliders if original probably are not in good shape. There are plastic slides (not the cylindrical insert) that wear out and/or break. If your seat flops or seems loose and tightening the pedestal collar knob doesn't take out the slop then the slides are most likely shot.
The bigger issue is the seat width. The 208 has a narrow helm and there are limited choices for seats that will fit. As far as I know, no seat with arms will fit the older 208s. The width issue is due to the fact that the right side spacing from the seat to the helm 'wall' is small and if the seat is not narrow, the seat may not clear the side of the helm and/or the seat will not be able to turn around. So make sure you measure the width of your existing seat and compare it replacement options.
I think there is a Todd seat that will fit. It may be this
Here is another choice for the boater that needs side entrance access to his seat.
www.toddusa.com
Note that seats do not include the slider mechanism