[marko69]

My car has seats like that. 1990 Porsche 944. In fact, any Porsche after 1985 has seats like that. Some don't have a power passenger seat, I think that was an option. Before 1985, many of the seat belt recepticles attached to the floor board. Look at the last photo's I posted, those are my seats. The seat belt reciptles attach to the seats, I just don't have them attached when the photo was taken.

Edited later:
Come to think of it, they don't fit your requirement since the seat belt strap is not attached to the seat itself, just the recepticle. I think a Chrysler Sebring convertible seat might work.