You can go to a paint store or large hardware chain store and pick up some of the paint sample cards. If you pick carefully you can find some that are about like the warm cards. You can also print your own on an inkjet printer on card stock and those work quite well. In fact, with the print your own method, you can try all sorts of different shades to get different color balances.
But I find it is often easier to just shoot RAW, and then you can pick whatever white balance you want when you do the RAW conversion.