>I was looking for New Left Review in Boston, hardly a backwoods
>rural outpost and a found a few scattered places which carry it.
>However, they were out of the current issue.
You're right that it's getting harder to find left periodicals in the stores. (Of course, the population of left periodicals itself is falling, but that's a separate issue.) Chains are part of the story - the decline of independents, both explictly left and not, means that fewer stores are in it for reasons other than profit maximization. Another problem is distribution; periodical distribution in general is a business full of criminals and incompetents. The Independent Press Assn list is full of complaints from people who've been fleeced by distributors, many of them smallish "alternative" distributors.
Any retailer run on principles of profit maximization is not going to feature the Brenner issue of NLR very prominently, despite the rare cover pictorial. Monthly Review redesigned itself to fit on bookstore shelves better, but B&N is not going to feature a magazine that looks like that, much less one that isn't merely socialist, but advertises it on the cover.
Which is why you should subscribe, Michael! Newsstand/bookstore sales are nice, but it's subscriptions that keep a publication going.