We don’t carry SMTSO-440-4ET from PEM. We do have a possible substitute from Keystone Electronics part # 4882.
Datasheet – https://www.keyelco.com/product-pdf.cfm?p=14254
The TechForum Cross Reference category is for parts that Digi-Key does not sell or parts that have gone obsolete. Our Engineers and Techs have reviewed the specifications for these parts and made a recommendation for a replacement. Please review the suggested part to ensure it will work for your application.