Though not directly related to situation you are in, you may quote para 36 of circular No. 125/44/2019-GST dated 18.11.2019 where even refund was allowed against 'invoices' which are not appearing in tax-payer's Form GSTR-2A when copies of such invoices were uploaded / submitted.
And, one need NOT even submit copies of invoices which are appearing in Form GSTR-2A for getting refund. As per said circular, the proper officer shall rely uponFORM GSTR-2A as an evidence of the accountal of the supply by the corresponding supplier(s) in relation to which the input tax credit has been availed by the applicant. Moreover, in said circular, it was emphasized that the proper officer shall not insist on the submission of an invoice (either original or duplicate) the details of which are available in FORM GSTR-2A of the relevant period uploaded by the applicant.
Using this logic, you should try & convince audit-officers that in your situation, they should accept photocopies of invoices presented by you for audit (which are anyway getting reflected in Form GSTR-2A).
If required, kindly tell them that you are wiling to self-certify these photocopies and wherever they have any doubt, you are ready to present even original copy of invoice.
This, I hope, will help you to avoid showing each & every in original (Here, I am presuming that you are having operational difficulties to present original invoice copies, but you have ALL invoices in original with you against which you had taken ITC).
P.S. One needs to try & see if there are any Dept's instructions / audit manual for its audit-officer/s in this regard.
These are ex facie views of mine and the same should not be construed as professional advice / suggestion.