The cam cover came from John Redmond:
http://jrcast.com/This comes with certain caveats; it took weeks and weeks, with all sorts of progressively more random excuses. It didn't come with a filler cap as I was told, and then through a series of phone calls found that it had been cast with a Honda filler cap fit, don't ask why....
Then, rather than the connected spout for the breather hose, the cover had been drilled and tapped with a 1/4" thread. This requires a 1/4" to 3/4" hose tail, which was tricky to find.
It comes in the metal and though it's not what I would call rough as a casting, required a couple of hours sanding to look good at a reasonable viewing distance, and that's after it was ceramic coated by Flying Tiger Coatings, who also had coated the sports manifold and are great.
You'd have to ask John if he does a Sigma cover, but expect something of a journey with it...... Good luck.....
