This adds another chunk of time to the project, but there is a way you could build the anti-reflection device (Real-life name for the honeycomb) using cardstock or something more durable. Essentially you'd cut a large number of strips of the cardstock as wide as you want the ARD to be deep (So probably no more than 1/4" wide) and cut slits halfway across each strip at regular intervals. It's important the slits be exactly half the width of the strip and at precise regular intervals, or else the pattern isn't regular. Hopefully these pictures can demonstrate both the concept and the dangers of not being precise (Though it seems you don't need any warnings about that).
I just cut up a sheet of regular paper, not bothering to be precise in the least, to give you a sense of what I'm talking about.
Here's one of the strips, with pen to highlight where I cut slits in it. You'll need a lot of these, and they'll need to be longer than the ARD is to be wide (I think about twice as long, but I'm not sure... That'll need some trial and error).
Here I've started fitting two strips together. As you can see, strip 2 is upside-down relative to strip 1 so the flaps of 2 cover the spine of 1 and vice versa. There's also a pattern you'll need to set up: As you should be able to see, strip 2 comes above strip 1, then goes below it again the next slit, then goes beneath a third strip the next slit, angles back up, comes above 1 again, goes below... I think you get the idea.
Here are four strips roughly thrown together. You can see how it's already forming the honeycombed shape you need,
and hopefully it's pretty clear how to expand this into a sheet that can cover your scope.
Like I said, it'll add a decent amount of time to the project, but I think it'd add another level of detail onto this already amazing project.
(PS: These devices are sold under the brand name of KillFlash in the United States for about $30 for a cheap one. This gets you the same effect for a very small fraction of the price!)