Many of the bolsters are hung on brackets and held in place by screws inserted through the grommets on the underside of the bolster. Try using very thin flat tool to slide between the fiberglass and the lower edge of the bolster. If you slide it and it hits something solid, you probably hit one of the screws. Poke around in the grommet hole for the screw head. There won't be a screw in every hole, just a few to keep the bolster from sliding up and off of the brackets.
Found the black end caps for the aft seat on Amazon as well. These bang into the end of the straight bar that installs into the (2) powder coated pieces. The bar moves up and down in the powder coated pieces when you fold up/down the seat. They make the seat slide easier.