If you look in the Body repair section of an Autopart store you might find a tube of something called Liquid Steel or Liquid Metal.
It is not really liquid or metal but it dries to be a hard silver colored plastic as described.
If the person who used it had degreased all the contact areas that the gasket is supposed to seal on the Liquid Steel might have worked to seal. However, I do not think it is made to take the Heat of an Engine.
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