Option 1) The cheapest option is using a front seat in the back, however that would require new bolt holes for the bases and they won't be Quick Release. This is what Adventure Vans in Charlotte does.
Option 2) http://www.cvcandmore.com/
This is the company that builds the Enterprise vans (mine was a former Enterprise Ride Share van). The older seats simply bolted to the stock rear seats holes, but they were not Quick Release. The newer CVC seats are all Quick release, but I believe they install their own seat track to allow this. CVC is in SoCal so shipping may be prohibitively expensive.
Option 3) Use actual rear captains chairs from Ford. This is the most straightforward conversion, since the bases use the same bolt holes for the bench seats. Also, they use the same hip point for the passenger side seatbelt quick release. These seats came in the Premium, Traveller, and Chateau trim levels. I have no idea what Ford charges for these, and they only come in leather now (older style seats came in cloth or leather).
Option 4) Toyota Sienna captains seats with rear seats bases from http://ujointoffroad.com/parts.html
. Chris is in Asheville. Best bet for takeout seats would be a mobility van converter. I suspect new seats from Toyota are $$$.