Hey, battle.net giftcards are very hard to find. They are also only available in these amounts; 20, 40, 60 and 80 euro. With that said, you won't find a giftcard for the amount of e*gold you currently have.
I had a hard time finding my own, while searching I found out that Epvp sells Battle.net giftcards in their official shop.
If you are looking for an EU giftcard I can recommend this website.
I bought my own key there
Goodluck finding yours!
