After searching (calling, actually) everywhere in Atlanta, it appears that no one (Radio Shack or ACK Supply) seems to carry the DPDT dual coil latching relay. Argh.
So, I've ordered it from Mouser. But I've got a gripe with Mouser... they do not provide a shipping price until they've actually shipped the order. So I have no real way of knowing what UPS ground is going to cost except for their rough estimate. I'm sure that estimate will be close, but it would be nice to have an actual shipping cost as part of the order before clicking the Submit button. Oh, well.
I've got to solder up that wire ribbon to the numeric keypad today... should take some time as the wires are very tiny and easy to tear.