How to get LAST card for Monster Summer Sale Badge?

Maybe it's silly, but this Badge only needs just one last card "Gold Helm", and I even can see some my friends have it. Steam offers me to trade them., but when I go to Trade Window I cannot see any Monster Cards in the friend's inventory not in my inventory as well. I can see them only on the Badge Crafting page.
From the looks of it trading for these cards has been disabled once the Monster Summer Sale finished, but I'm just speculating here. Can somebody confirm that?
And if yes: Is there any option to obtain this last card?

steam-monster-game

Best Answer

I looked into this yesterday as well, and I believe they're disabled completely. I do not know of any way to unlock these cards, or buy/trade them. I wanted to sell mine, since I only have two of them, but I cannot.

Unless there is some special way to do it, or they unlock them for next summer, I don't believe there is a way.