Lap-diagonal belts all seats?
 

I am planning to buy a -02 Trajet, but this model lacks a lap-diagonal belt in the middle row, middle seat.
Does anyone know if it is possible to exchange this seat for a newer one, let's say from a -05 with a lap-diagonal belt? My Hyundai dealer can't answer the question, and neither can the garage.

If the seat fits, it would be a great way to increase safety without having to buy a newer, more expensive car.

If you know anything about this, please let me know!

Dimaz in Sweden