HP lists this spare part number for the HP EliteBook 840 G5 Healthcare Edition in its Maintenance and Service Guide (printed p.23).
Source notes
HP Maintenance and Service Guide for the HP EliteBook 840 G5 Healthcare Edition (Document Part Number L12741-001), spare parts table, printed p.23: "256 GB, SATA-3, Opal 2, TLC L29191-001". Read from the cached HP manual (via FDY-MM-015-K5).