Ask away - it will be interesting to see what turns up.
The 2-1 inlet manifold has the carb level.
But not sure I've seen anything like Commando style manifolds - but for an Atlas- like that, for twin carbs.
I had a local engineering shop fab up some custom manifolds recently (not Atlas),
I'm sure if you greased someone palms they could do you a pair. ?
Be quicker/easier with straight tubes and angled endplates than curved tubes though ?
Armours do siamese pipes for some models of dommies (early 1960s they were a factory option)
so whether they would fit an Atlas is an interesting question.
You tried the usual suspects - Walridge And do Rabers and BritCycle still trade ?