Has anyone found a solution to this? I'm in the same spot. Everyone says "acid-free" everything...so far I've found great solutions for the bag (Mylites2), boards (fullbacks), and even good microchamber paper for inside the comics (from conservationresources.com), but no sensible solution for the comic box.
Much like this post, I was going to go with the box 13 from Egerber.com, but they said they're out and won't get anymore until next year (and wouldn't be more specific about WHEN next year). The Bill Cole boxes are WAY too expensive. I saw the same boxes you did at Hollinger Metal, but they're about as expensive as BC.
I'm curious about the microchamber boxes at the conservationresources.com site. If it's the same material that removes acidic and other pollutant qualities as the paper you put inside the comics, wouldn't it stand to reason that it would also help with that if the box was made of the same material? It's very expensive also though. Anyone have any thoughts?