You might be able to take a cast valve cover and cut the top off and then weld on a plate with some holes in it for the clear top. That seemed like a lot of work to me so I just made the valve cover from billet and drilled and tapped it for a bolt pattern then cut out a top from 3/16 thick clear polycarb. My first attempt used a gasket but it always leaked so then I just used RTV to seal the clear top on and I haven't had any leaks since.