VMware PowerCLI, PowerNSX Determine External IP of VM

I'm looking for a way to determine the external IP address of a VMware VM using PowerCLI or PowerNSX.  I'm currently using PowerCLI to query a vmware environment and record VM details to a database.  External IP's in my environment are configured in NSX via NAT.  I had originally thought I could use Invoke-WebRequest and Invoke-VMScript however it that would require authenticating against the guest OS which I cannot do.

How can I query NSX to determine an external IP?

Expert of Script:

$VMs = Get-VM | Select *
$VMGuestInfo = Get-VM | Get-VMGuest | Select *
# Inserting each row
ForEach ($VM in $VMs)
{
$VMID = $VM.ID
$PersistentID = $VM.PersistentID
$Name = $VM.Name
$PowerState = $VM.PowerState
$Notes = $VM.Notes
$Guest = $VM.Guest
$NumCpu = $VM.NumCpu -as [int]
$CoresPerSocket = $VM.CoresPerSocket -as [int]
$MemoryGB = $VM.MemoryGB -as [int]
$VMHostID = $VM.VMHostID
$VMHost = $VM.VMHost
$VApp = $VM.VApp
$FolderID = $VM.FolderID

$FolderPath = Get-Folder -ID $VM.FolderID | Get-FolderPath

$ExternalIP = ???
$Hostname = $VMGuest.HostName