"The FCRA doesn't apply to the original creditor. It only applies to collection agencies."
That's incorrect, and I'm guessing you're confusing the FCRA with the Fair Debt Collection Practices Act. As is relevant here, the FCRA is generally applicable to both original creditors and to "debt collectors" to the extent they are "furnishers of information" to one or more of the credit reporting agencies. Section 623(b) of the FCRA imposes certain requirements on a "furnisher of information" upon receipt of a notice of dispute pursuant to Section 611(a)(2).
However, for the original poster, nowhere in Section 623 is there a requirement that a "furnisher of information" provide the results of its investigation to the consumer. Accordingly, there's no prohibition on the "furnisher of information" charging for copies of documents.