There is no other way except buying anything either the card is okay or not. The OP is trying to give the card as collateral so it is impossible to check by the lender either the card is valid or not. Also same will happen if use escrow. From borrower/lender/escrow may use card and deny the use of the card.
It would be reckless to accept what the OP is offering as collateral for a loan. However, the OP has indicated that he no longer has any use for the value of the credit in his Amazon account, so he could effectively sell this credit to someone in order to realize the value of the credit.