For a short term DIY gasket fix, try some sheet gasket material from an auto supply.
The OEM cover gaskets are rather thick but that may not be a real concern. Xacto knife and an approprate diameter bit of tubing - brass, steel, alum - with an edge sharpened on the outside of the tube will make a neat hole punch.
Remember that the valve covers do not require a gorilla-strength tightening... especially the center stud. Perhaps a light brushing of a gasket sealer will keep oil inside. These gaskets don't have a notion to leak very often anyway.
Order a fresh pair while you're putting around on the home brew version. [smiley=thumbsup.gif]
Monte