houser,

If you look in the shop manual available in the download section, that bolt is called the 'Rear Seat Hinge Fixing Bolt'. Pix are on pages 8G-4

It looks like the parts manual lists it as part# 89438 46970 if you wanted to try to order some from Merlin.

I'll see if I can pull one of mine & run by Lowes to see what size it is.

Tom