Thank You Meatstick!!
Mrs Bear gets that sauce at either of our local stores (Giant or Weis).
It's called Talarico's Sandwich Steak Sauce, and we've been using it on Cheesesteaks for about 40 years.
It is a Tomato based sauce, but it tastes just like most of the sauces used in this Philly Area at our Steak Shops.
You can search "Talarico's Philly Style Steak Sandwich Sauce", and their web site comes up, and has a bunch of other sauces too.
I'd give you the link, but it's not a good thing to do on the forum, and it's easy to find.
Bear