Another suggestion is to take a plastic container, fill it with water, and add your credit cards, then pop them in the freezer so they are in a solid block of ice. They are still with you, but it will take a while for the ice to melt so you can use them. A cure for impulse buys, but they are there if you really need them.
I don't remember where I read this, but it sounds like it might work for you.
