Check the local stores again, this time look for the section where the keep the gallon jugs, you are bound to find either Shell Rotella (15-40 with all current diesel specs) and Chevron Delo 400 (15-40 w/ all current diesel specs). And I think I even saw Autozone branded 15-40 oil too, although I didn't check for specs. (same goes for Discount Auto Parts chain here in Fl).
On my 300D, requiring 8qts, buying 2 jugs sure makes changing oil a breeze.
And, if you're a treehugger (no offense), you end up with less plastic waste too!
03/83 300D 184k
07/73 280 160k