With no sling and no sewing machine, and my parents unwilling to sacrifice a bedsheet, you'd think I'd be fucked. But not so fast!
A trip to Wal-Mart (EW. But my only option) and I'm re-slinged. I used two yards of a thin cotton knit, folded lengthwise (to double it) and knotted at the shoulder. Knits have stretch (and this fabric was quite flimsy, even with the doubling), so I had to keep tightening the knot as the fabric got more and more stretched out. Once it got stretched out all the way it was quite comfortable and forgiving. And I didn't even use scissors!
It would have been even better if Wal-mart had a set of heavy-duty metal rings in their hardware section. But alas, no rings, and none of the shower curtain rings I found were sturdy enough for the job. I plan on purchasing a set of rings because I'm kinda jazzed about my new stripey orange sling.
Another option would have been a wrap style carrier, a la moby or Ellaroo. I've done this before, back when Naomi was about a year old. I bought five yards of rainbow tie-dyed fleece (because it was cold outside) and cut it into a strip 25 inches wide. At this width, you could make two carriers. Cut it 20 inches wide and you could get three carriers, but the width would be too narrow for a safe back carry.