I understand your wanting 3 point belts in the rear. Factory parts for that are extremely rare. Have you considered installing rear seat belt assemblies from a later make/model ? Honda maybe ? Good luck
I like to keep things factory looking, often changes need to be certified down here too. Aslong as I can get some factory rear floor anchors I can use any sort for the shoulder belts atleast. Im kinda obsessive about using factory parts. :)