For the light baffles, I cloned the old Corona. It had two strips of thin brass, folded into long "vee's", with a narrow strip of black velveteen glued onto each strip. (I used ordainary 3/8" wide black velveteen ribbon from Fabric Land). They were set down into two parallel grooves, and acted just like the spring action weather stripping on a typical good quality front door. The brass can't be over 0.002" thick, or the insertion force for the darkslide will be too great.
I used 0.032" Garolite. It's a bit thin (I wish it were available in metric thickness, 1 mm would be perfect. By being careful about the spring action on the baffles, I can keep the insertion force low enough so the 1/32" Garolite won't try to buckle. Another advantage is that the total weight of the holder is kept down to a svelte 2lb-3oz, compared to 3lb-6oz for my Blunderbuss Wisner holders.
I got the bookbinders cloth from a local bookbinder (of all places). I picked up a few samples to try, and decided on a pseudo "leatherette" texture on a coated cloth that's 0.012" thick.
Here's a photo of my efforts...