Middle row bucket seats for Expedition?

I have a 98 Ford Expedition with a middle row bench seat. I plan on keeping the truck for many more years, and the problem is that my growing teenage son is finding it harder and harder to get back to the 3rd row seat. I would like to replace the middle bench seat with a pair of bucket seats. Does anyone sell this conversion? Did any year of Expedition come with middle row buckets that I may be able to find in a salvage yard? Any advice would be appreciated!