I am having trouble finding replacement boat seats. I have a older 1991 or 1992 25' four winns. The lounger boat seats on it have an 18" base, I am replacing the seats, and cannot find seats anywhere that are higher than 12". I'm wondering if these were custom made since I bought my boat used. Does anyone know where or how I can find seats with a tall seat back, and an 18" H base?