Is The Dark Bros. (Gregor Dark, Greg Dark) pornography available in some kind boxed set form? I've reached out to the Criterion Collection several times to no avail.

I doubt there's a boxed set, but the people at The Vinegar Syndrome have put out a bunch of Blu-ray releases of tons of niche films (including adult) from the 60s-90s. Wouldn't surprise me if New Wave Hookers or something like that were in there.