How can I programatically allocate AWS private IPs

I'm using the HA_Across_AZs iApp to create pairs of virtual servers in an HA pair that crosses AWS availability zones. The iApp asks for an EIP (public), and a private IP in each AZ from the corresponding external-facing subnet. I'm trying to automate this process using Ansible. I see how to allocate EIPs with ec2_eip, but don't see a corresponding function for private IPs. The only thing I do see is that a private IP can be requested when an instance is created, but since it's a BigIP that already exists, I'm not creating anything. I presume it would be considered a secondary IP on the external facing interface, with the primary being the external-facing self-IP of the device.

Does an ansible module exist for this function, either from F5 or AWS? Or a different way to accomplish the same result?