You can try
https://www.reddit.com/r/giftcardexchange You can easily get a amazon or ebay card for ~75% in cryptos.
But you need to have a good rep at that sub to be able to go second.Try to trade with the mods(if they are selling).How much amount you looking for?Because you can buy only upto 100$ on that sub.
Sometimes even I have amazon cards, 80% is a pretty good rate.I will hit you with some, are you looking for long term trade, or just for now?
And beware of scammers.Good luck