Last time I was in the Gamestop near me there was a weird dude hanging out by the counter asking people to use his gift card to make their purchase and then give him the cash afterward. I did it. He had like $53.xx on there and let me just give him $50 for it, plus he let me make the purchase on his card first before I gave him money so I would know it wasn't a scam or anything. I wasn't going to complain since I was about to spend the money anyway.
So, uh, yeah, I guess one solution is to creepily solicit strangers and hope the employees don't care.