What a great compliment. But never, ever leave your portfolio no matter how much you want the position.
Once your portfolio is out of your hands, you have no idea how it's going to be handled. Portfolio cases can easily get damaged and even lost in an office. You don't want your portfolio to end up stuffed in someone's inbox with papers all over it while it also serves as a coaster for morning coffee like the one in the picture above.
You have a couple of options so you don't offend anyone. You can say you would love to schedule another appointment to show your portfolio. Or you can even say you'll be happy to fax over a copy of your portfolio, which is basically a black and white copy of all of the materials you've shown in your portfolio.