Where to buy new seat bases?

[Chaparral 2500]

Older boats have wooden bases for back to back seats and they rot/disintegrate over time. Where can the newer fibreglass/plastic/composite ones found in current boats be purchased to re-fit an older boat? I have looked for hours on dozens of supplier websites and found nothing. Contemplating going to George's Salvage to look, but I want nice looking ones. Any advice appreciated.