I've used 3~5 wraps of painter's paper tape as rim tape for tubed tyres and it has held up well.
The trick is to have the right width of tape such that it fills the valley in the rim without getting into areas where the tyre bead should hook.
No amount of protection will help if your spokes are already poking through the end of the nipples, so if there's any edges detectable by your fingers, then get in there with a file and make it smooth, and finish with sandpaper. Clean out debris well before reassembling. You generally don't need to protect the bare metal because it will be brass or aluminium or stainless steel. Only steel needs protection from corrosion,
Also deburr the edge of the valve stem hole with a hand scraper and not with an oversized drill bit.
The pressure of air in the tube should hold your tape in place - and the valve stem limits the distance around the rim that the tape might migrate.
Second option is that plastic strapping tape which holds boxes to pallets for shipping. Not the metal version. Lay a length in, overlap it, and make a hole through the overlap for the valve stem. You should also tape it down. (see comments)
Finally if you're caught really-bush, then look around for some flax-like plant and use some leaves. It won't be great and will stain, but should be enough to protect your tube till the next town.
Then find the LBS in the next town and talk to them. Amazon really isn't the best source of bike parts specially if you're touring.