I think WWOHP is probably the only place in both parks where you can't get pressed pennies. It wouldn't make sense with the theming anyway. They could possibly put a machine in the Emporium up front of IOA that sells a lot of HP merchandise, but I can't see a machine like that ever finding its way into Hogsmeade with the iron fist JK Rowling and WB control it with.
That said, I spent the last two days introducing a nephew of mine to pressed pennies and there are a lot of great ones there. One of my favorite machines was in the main store at US and has a fantastic Jaws, King Kong and ET design. Many of the areas have two pressed penny machines with different designs, so there is an opportunity for a lot of pennies (which is good, because the pressed penny book we bought for him at Universal has a ton of slots!)