Very easy for the prepared sort. Have a five-gallon bucket and plenty of 13 gal. kitchen garbage bags. Have the seat and lid that snap onto the bucket top tucked away somewhere for just such a time as this. Hang a roll of paper on one side of the wire bucket handle. Have cat litter, charcoal, fir or pine needles, saw dust, etc, for absorbent and covering material. Presto! Your bathroom is ready to use in five minutes or less.

Now to be more honest - my knees will not permit me to sit on that height, and I have not yet figured out what I can place the bucket on that will bring it to the correct height, and be solid enough not to slip around or cause me to fall. Ideas, please?