You cry yourself to sleep every night after trying to get the black keycard for 8 hours straight?
You can't put any loot in your stash because the military batteries are taking up all the space? Worry not, a fool proof.
Step one: get all the items ready.
Step two: get to the flea market page before the trade reset. Make sure to enable the only trades to be from traders and save settings.
Step three: wait for the reset timer to reach zero. It will instantly say " sold out" , but it's not, it's restocking.
Step four : you want to refresh as fast as possible and hold your finger on y to accept the trade.
Now, refreshing is slow if you do it with f5 or the little circle, but there is a different way.
If you click any of the buttons reading "expires in" "price" "offer" or "merchant" twice, the market will also refresh.
What you want to do is hit Refresh, click all the buttons twice shortly after one another and repeat. When the trade comes up click buy and be happy.
Worked on the first try, and I hope it works for you so we can stop posting about it 12 times a day.