I’m thinking of fabricating a metal strap like those used to hold fuel tanks to bolt onto one of the bolts on the oil gallery cover and an exhaust manifold bolt

 

Ebay has 862's for $135 each. Pretty cheap!

 

It isn't that much effort to put a new head on.
Buuuuuut, if I wasn't removing the head, I would make a stiff L or C shaped bracket that would bolt to the side of the head with a nut on the end so I could thread a bolt thru it to hit the valve cover and push it down.
Sloppy style.

 

To each their own, but in my h-o, that would be a cobble job. Your engine, your choice....