I don't think rolling up a card in your lap will go unnoticed.
If I recall, there is a bill in lemon for a signed bill on L&L's Greatest Magic Bill in Lemon DVD. My recollection is that the method works but eally isn't worth the effort. If you are performing with someone else, it would be a lot easier.
Honestly, the torn corner is more powerful than you are giving credit for. It gives a great visual for the audience to see the corner fit AND you don't even come near the orange.
The other idea is to use the method for a card in ring box (See Books of Wonder, Volume 1) and two spectators -- one to pick the card and one to cut the orange. You should be able to figure out the rest.