Retractable Seat Belt Parts??

['72 C10 Super]

My passenger retractable seat belt does not retract. I took it apart and
the clear plastic outer part is completely broke and a dozen pieces came tumbling out. The inner part that has the spring is fine, but I need the outer part to keep the inner spring tension in place for the retractor to work.

Where can I find the outer clear plastic part?

Thanks,