Funny, I was thinking about this the other week for my Holga - like you, I want the lens effects, but not the light leaks, and did some searching on any sort of Holga "neverready" case, but came up empty.
I might be willing to part with $5-10 for a Holga version of this, but then again I might be in the minority there
(I'm assuming the material is not leather or anything expensive, as that would be kind of anti-thetical.)
Actually if you already *do* have a Holga version of this, PM me and I might take it off your hands.