I ended up writing a powershell script to log in to the PSC and actually add the source. It's not the cleanest, but it works.
good luck. (just updated one part).
Powershell:
$ie = New-Object -com InternetExplorer.Application
$ie.visible=$false
$ie.navigate("https://<FQDN of PSC>/psc/")
while($ie.ReadyState -ne 4) {start-sleep -m 100}
while($ie.document.ReadyState -ne "complete") {start-sleep -m 100}
$ie.document.getElementById("username").value = '<SSO Admin User>'
$ie.document.getElementById("password").value = '<SSO Admin Password>'
$ie.document.getElementById("submit").Disabled = $false
$ie.document.getElementById("submit").click()
start-sleep 10
$ie.navigate("https://<FQDN of PSC>/psc/#?extensionId=sso.identity.sources.extension")
$ca = $ie.document.documentElement.getElementsByClassName('vui-action-label ng-binding ng-scope') | select -first 1
$ca.click()
$ie.document.getElementById("adType").click()
$ca = $ie.document.documentElement.getElementsByClassName('ng-binding') | ?{$_.innerHTML -eq "OK"}
$ca.click()
$ie.quit()
