Yamaha calls it: Cover, Footrest 23P-27413-00-00
Partshark wants $7.54 each + shipping. Ebay has them for about $15 shipped, though you might get a break on shipping when ordering Two. Search on the part number for quicker find.
Didn't see any used ones. Good luck on finding some take offs that someone is willing to part with. Maybe ADV?
Hey, take a second to add your location to your profile. State (or country if outside the US), is good enough. I know you told us when you did your intro, but everyone forgets quickly.