Issue using ADSI in powershell to load users from another domain into a group

Question

I am trying to load users into a domain local security group from another domain using ADSI and powershell. For users who have an existing foreign security principal I can load that without issue, but the users who do not have a foreign security principal
I am unable to load.
These work fine, assuming the group domain is fabrikam:
$Group.psbase.invoke("Add",[ADSI]"LDAP://CN=$external_user_sid_who_has_a_FPN,CN=ForeignSecurityPrincipals,DC=fabrikam,DC=com")
$Group.psbase.invoke("Add",[ADSI]"LDAP://$userDN,DC=fabrikam,DC=com")
These does not:
$Group.psbase.invoke("Add",[ADSI]"LDAP://CN=$externaluser_sid_who_does_not_have_a_FPN,CN=ForeignSecurityPrincipals,DC=fabrikam,DC=com")
$Group.psbase.invoke("Add",[ADSI]"LDAP://<SID=$external_user_sid_who_does_not_have_a_FPN>")
$Group.psbase.invoke("Add",[ADSI]"LDAP://<SID=$external_user_hex_sid_who_does_not_have_a_FPN>")
Any help would be greatly appreciated.
Thank you

Answer 1

Thank you for your reply,
I started with that thread and it ultimately recommends using the [ADSI]"LDAP://<SID=$hexsid>, this bind is not working for me. The page it points to for conversion of sid to hexsid is in VBS, but I have used the below powershell to duplicate its function.
$sid = "S-1-5-21-2127521184-1604012920-1887927527-72713"
$parts = $sid.Remove(0,6).Split("-")
foreach ($part in $parts)
$hex = ([Convert]::ToString($part, 16)).ToUpper()
While ($hex.length -lt 8)
$hex = "0" + $hex
for ($i=1; $i -lt 5; $i++)
$reverseEndian = $reverseEndian + $hex.substring($hex.length -2, 2)
$hex = $hex.Remove($hex.length -2, 2)
$hexSid = "0105000000000005" + $reverseEndian
For example SID S-1-5-21-2127521184-1604012920-1887927527-72713 needs
to be turned into raw hex sid 010500000000000515000000A065CF7E784B9B5FE77C8770091C0100 according to that article and
then put in the ADSI bind like this: [ADSI ]"LDAP://<SID=010500000000000515000000A065CF7E784B9B5FE77C8770091C0100>". 
When I put that bind in (with an actual sid and not an example sid) I get the following error:
format-default : The following exception occurred while retrieving member "PSComputerName": "There is no such object on
the server.
+ CategoryInfo : NotSpecified: (:) [format-default], ExtendedTypeSystemException
+ FullyQualifiedErrorId : CatchFromBaseGetMember,Microsoft.PowerShell.Commands.FormatDefaultCommand
For users who are on another domain but already have a foreign principal name created, I can add them easily enough by converting their sid to the appropriate foreign principal name format. I haven't yet had any success adding someone who doesn't have a
foreign principal name though, even after trying the solution referenced in the article.
Thank you in advance for any help.