VPN connectivity from AWS to a Physical Data Centre

VPN connectivity from AWS Cloud to a remote data centre CISCO ASA 5500 device Want to create a VPN device on Amazon Cloud such that the configuration file of the same can be given to a physical data centre to configure it at their end so that VPN tunnel can be established. The data centre doesn't want to use the Private IP of AWS for VPN Tunnel. Instead they want us to give our side Public IP instead of Private IP that has to be NATTed with our Private IP If anyone has done something similar