How can I replace this SMD diode?
The chances are good that this is a 1SMA4742 12 volt Zener diode.
The datasheet is from a different manufacturer, but I'm pretty sure it is the part you need.  Other companies that make the 1SMA4742 also mark them &quot;472.&quot;
The &quot;PG&quot; is probably a date code.  The comment from tlfong01 suggests it might be code indication packaging material.  That may well be true.

From looking around, it seems the 1SMA4742 is a surface mount version of the 1N4742 12V Zener diode.  The 1N4742 comes in a conventional through hole housing, and may be more commonly available.