Many have suggested shallots, but can you buy a single shallot? I only see them in bags of a dozen or so, probably much more costly and wasteful than a single RO? Wrapping half an onion tightly in clingfilm (sarin?) gives it a fridge life of about 5 days, I find.
IMO dried onions are a completely different animal, and unless you need their particular presence (onion soup, maybe?) you would be better just to omit onion from the recipe.
