Monzared:
Have you ever seen any STI`s at an auction from a collector, like those collector vehicles that show up on Barrett-Jackson`s or Mecum`s?
I cannot remember ever seeing one, but you never know unless you ask those auction houses them to keep an eye out and contact you about one.
I would also let on-line car dealers like Carvana or Vroom know you are interested in finding one. They would be a more likely cheaper source than an auto auction house, but your criterion for an ultra low mileage (<5,000) vehicle of those vintage years (2004-2007) make it, as your topic title states, "a needle in a hay stack".