Morwenna
I bought two mini decks years ago just so I could do this, and I never did... But now I have another small deck, and I started carrying that one around, but I haven't been consistent. The two older decks are the Grimaud Marseilles and the RWS; I can't use the Marseilles right now becuse one of the cards has gone missing (a Major at that), and anyway I never learned that system. But the RWS and the Hanson-Roberts (the newer small one) do get into my purse or pocket once in a while now. Not that I've given myself any chance to use them while I'm out, you understand...