If the hull is old, you will be hard pressed to find cushions that fit, especially fit the snaps. So you have two options: Have replacements made and that can be pricey or buy replacement seats with cushions. The second option may turn out to be less expensive than having cushions made.
Note that the 208 has pretty narrow seats and the choices for replacement are fewer but possible. The Todd Chesapeake model is one that will fits ( If I remember correctly) and there are cushion sets available for it.