Weatherproof z-wave doorbell button?

I purchased an Aeotec Doorbell with the intent of not only using it as an audio notification device, but actually as a doorbell as well. Unfortunately, the building I am installing it in has metal siding panels that prevent the wireless doorbell button from communicating with the receiver. Does anybody have any relatively low cost solutions that might serve the purpose of being an exterior, battery-powered button that would trigger a ST event from which I would in turn trigger the Aeotec Doorbell? And, FYI, there is no existing doorbell wiring of any kind. Thanks.