I have been looking to add an L shaped settee to ours. Right now it is wide open. All I could find were pontoon boat type seats which were overstuffed, striped, etc. and didn't really match the boat. I looked at the well known marine salvage/consignment places here in South Florida but couldn't find anything so I will be interested to see what you come up with!
Lots of opinions on whether or not adding is a good idea. No adjustment of seating, deck camber causes install difficulty, etc. You already have it so you are aware of these "issues". Is the settee you currently have original to the boat?