An "armoured hesalite crystal" is a plastic crystal with a metal compression ring (gold or silver). Original Omega crystals would be ordered by case reference number (on inside of case back) not by caliber number.
If you know this number you can order an original Omega crystal (or a generic) from a watch material supply house like Otto Frei or Jules Borel. Note that to install this type of crystal a special tool called a "crystal press" is required.
Perhaps you should take your watch to a watchmaker to replace the crystal?
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