Purchasing rear seats for extra passengers

Is it possible to install a middle seat in the second row of a seven seater 2004-2010 Sienna to make it an eight seater? Most Siennas are seven seaters, but I am hoping a quick junkyard trip can yield another seat.

Mine is a 2003.
I don't have any mounts in the floor for anything else to go there.
I have 2 bucket seats for the middle row and a rear bench seat.
You will need to check to see if there are any mounts to add another seat in your van.