hi and
Magnetnerd
You can usually get gaskets making paper/card, usually the colour is brown and comes in various thicknesses from car accessories or motor factors or possible some bike shops,
Don’t try using normal paper or card as these are no good.
Making the gaskets, one way is to cut out a bit of gasket card and lay it over the part you want to make the new gasket for. and using a small ball head hammer tap lightly around the edge of opening were the gasket will seat and hopeful you have a new gasket !!.
As for the head gasket I wouldn't try to make one of these, get new one from your dealer.
The valve cover, you more then likely will not get paper the right thicknesses or size of paper to make one up, if the old one is still ok you should be able to reuse it, or again new one from your dealer.
Dek.