There is a Custom Operator: Get CI Details Process . This is part of the 'CA IT PAM Workflows - Pre-built for CA Service Desk Manager' from the Best Practices page.
Or you can use the 'Base Select ServiceDesk Elements Operator' from the 'CA Service Desk Connector Guide' (on which the above is based). You want to specify 'lrel_asset_chgnr' as the ServiceDesk Object type and '"chg=" + <your change order id variable>' for the Where Clause.
-Jeff