You can basically get a different
SIM card anywhere. There are both pay-as-you-talk and monthly plans that you could buy. If you are a frequent traveler, I would use the pay-as-you-talk method. You could buy a
SIM card for your phone, and replace it whenever you need your "other" number or you are going out of the country. Just do some internet research and I bet you will come up with some good deals!