I just used zinc plated bolts. What actually looks better is allen key headed bolts. A place in on Sinclair Rd, Dandenong, Vic makes them. I am sure they'd be available somewhere in NSW.
<==thats what my engine looks like with the zinc plated bolts. They are hardly noticable.
My only word of advice on these rocker cover is don't over tighten them. As you'll fracture the cover and snap about 1/3rd of the cover off. As silly as it sounds yes it will and can happen. They crack the covers around the long bolt area.