Question about the bar the seat belts attach to.

[LuckyScott]

So I put the third row seat in my 72 Burb. If I am going to attach the two middle seat belts I need to drop the gas tank, and drill the holes thru the floor.
But I also have a 72 Blazer and that has a bar that goes across the back of the back seat that attaches to the outer brackets, and then the two seat belts in the middle of the seat attach to that. No holes in floor and easy to attach the belts.

Does anybody know where I can find this bar? I guess I could make it myself, but if it is a factory part I would rather just find the factory part.