So, I really like the ProMaster double passenger seat option, but didn't want a ProMaster because I wanted a reliable van:)
So what to do:
Buy Ford Transit double rear seat, because they're super inexpensive. They come in two widths, 32" and 36". The 32" is really narrow for adults, but would leave a small 4" gap between the seats that maybe a skinny person could squeeze through? In any case, I bought the 36" because there is just enough space to fit it and it's more comfortable for adults or two kids who fight if they are touching each other.
I'm not quite finished with painting or all little details, but attached is a functional seat, as I am using it now.
You'll also need to fake the passenger seat airbag. I bought the needed connector out of some other Nissan passenger car at the junkyard for ~$5 so I wouldn't have to cut wires. Soldered the resistor to the new connector, plugged into seat harness, and no airbag light.
Like the ProMaster double seat, the Ford seat is not adjustable in anyway.