Personally, I think this could be a good option for someone just looking for lap/shoulder belts, and doesn't mind not being original.
I'm just throwing it out there as an option - I am not associated with the seller or the offer in any way.
For a Lap & Shoulder belt setup, you would have two belts mounted on the inside of the seat from the same attachment, by the console.
These belts are non-retracting, and you would have to fabricate "mounting eyes" for the attachment clips.