A proxy command of PowerShell's New-WebServiceProxy to allow for the passing of client certificates during creation.

New-ProxyWebServiceProxy.ps1

Function New-ProxyWebServiceProxy {
    [CmdletBinding(DefaultParameterSetName='NoCredentials', HelpUri='http://go.microsoft.com/fwlink/?LinkID=135238')]
    Param (
        [Parameter(Mandatory=$true, Position=0)]
        [Alias('WL','WSDL','Path')]
        [ValidateNotNullOrEmpty()]
        [uri]
        ${Uri},

        [Parameter(ParameterSetName='Credential')]
        [Alias('Cred')]
        [ValidateNotNullOrEmpty()]
        [pscredential]
        [System.Management.Automation.CredentialAttribute()]
        ${Credential},

        [Alias('Cert')]
        [ValidateNotNullOrEmpty()]
        [System.Security.Cryptography.X509Certificates.X509Certificate2]
        ${Certificate},

        [Parameter(Position=1)]
        [Alias('FileName','FN')]
        [ValidateNotNullOrEmpty()]
        [string]
        ${Class},

        [Parameter(Position=2)]
        [Alias('NS')]
        [ValidateNotNullOrEmpty()]
        [string]
        ${Namespace},

        [Parameter(ParameterSetName='UseDefaultCredential')]
        [Alias('UDC')]
        [ValidateNotNull()]
        [switch]
        ${UseDefaultCredential}
    )
    Begin {
        Try {
            $outBuffer = $null
            If ($PSBoundParameters.TryGetValue('OutBuffer', [ref]$outBuffer)) {
                $PSBoundParameters['OutBuffer'] = 1
            }

            If ($Certificate) {
                $TempFile = [System.IO.Path]::GetTempFileName() + "_wsdl.xml"

                $WebRequest = @{
                    "Certificate" = $Certificate
                    "URI" = $URI
                }

                If ($Credential) {
                    $WebRequest.Credential = $Credential
                    #$WebRequest.ProxyCredential = $Credential
                } ElseIf ($UseDefaultCredential) {
                    $WebRequest.UseDefaultCredentials = $True
                    #$WebRequest.ProxyUseDefaultCredentials = $True
                }

                $Response = Invoke-WebRequest @WebRequest
                $Content = [XML]$Response.Content
                $FirstChild = $Content.FirstChild

                If ($FirstChild.Name -eq "xml") {
                    $Content.RemoveChild($FirstChild) | Out-Null
                }

                $Content.OuterXml | Out-File -FilePath $TempFile
                $PSBoundParameters.Uri = "file://" + $TempFile
            }

            $PSBoundParameters.Remove("Certificate") | Out-Null

            $wrappedCmd = $ExecutionContext.InvokeCommand.GetCommand('New-WebServiceProxy', [System.Management.Automation.CommandTypes]::Cmdlet)
            $scriptCmd = {& $wrappedCmd @PSBoundParameters }
            $steppablePipeline = $scriptCmd.GetSteppablePipeline($myInvocation.CommandOrigin)
            $steppablePipeline.Begin($PSCmdlet)
        } Catch {
            Throw $_
        }
    }
    Process {
        Try {
            $Proxy = New-WebServiceProxy @PSBoundParameters
            $Proxy.ClientCertificates.Add($Certificate) | Out-Null
            $Proxy
        } Catch {
            Throw $_
        }
    }
    End {
        Try {
            If ($TempFile) {
                Remove-Item $TempFile
            }
        } Catch {
            Throw
        }
    }
    <#
    .ForwardHelpTargetName New-WebServiceProxy
    .ForwardHelpCategory Cmdlet
    #>
}