I do not know anything about Super 8. But there is a thread here on it here:
and more on Super 8 in: https://originaltrilogy.com/topic/An-Index-Help-Thread-for-Original-Trilogy-Discussion/id/57363
Specialist Super 8 websites, or film collector websites, will likely have more information on how to buy them.
If any are still available, or not massively expensive?