Went back to the co-op today to try again at crank replacement. It
was open! To my great surprise, the SR Custom (Super Custom? I
forget) crank I had previously been eyeing off was no longer there.
However, also to my surprise, I found that the other offerings didn't
seem as ugly to me as I recalled them being. I grabbed some fairly
generic looking 170mm Shimano crank without any apparent special
branding, and installed it "the proper way", i.e. with greased spindle
and a second tightening of the bolt after an initial ride, to
counteract the loss of preload. Time will tell how this holds up. I
*really* hope it proves reliable. Autumn is well and truly into swing
here and I worry that I may only have another month of good riding
opportunities before it gets too cold and/or dark...