I have a 13" Swivel-Eze non-adjustable post and standard spring cushioned seat base I found in my shed. It was replaced by my dad for an adjustable height post when he owned the boat. Yes it is 2" taller than the ones you normally find at Academy or Walmart. He is a tall guy and it worked well for him for the most part.
I don't need it as I use a leaning post up front and I still have the adjustable one in the back for guests.
$15 and it's yours.
I can meet FTF in Fort Worth most afternoons.
'99 Skeeter 186SX SC, 150 Yamaha VMax
'13 Ford F-150 SCrew XLT, 4x4, 5.0, 6-spd