Authentic or not, you can have a good cheesesteak without murdering a ribeye. We have a butcher in the local farmers market who sells thin cut steak meat by the lb. I wish I knew what cut it is, I'll have to ask him next time, it's definitely not ribeye though and it's still makes for a good steak.
I like mine with American cheese, sauce and onions, I like to call them suburban cheesesteaks since that's what most of us in the burbs are used to. When I'm in the city though, it's Wiz Wit for sure.
Here's some semi-authentic inspiration I entered in a TD a while back, I lost to a farking Aussie if you can believe that!
BTW, if you haven't had a Schmitter, you might want to look into that too.