I've got a DIY for a simple bucket toilet listed elsewhere on this site, but don't underestimate the power of comfort in a time of crisis or need.
The Luggable Loo bucket toilet lid is perhaps one of the best $12 bills you may spend while prepping.
Anyone who has been on an extended camping or backpacking trip can appreciate the simple joy of returning from the woods to a comfy commode.
Sadly, when the shit goes down, so will your shitter. Picking up a pre-fab seat for your bucket toilet will make the daily act of bagging into the bucket a bit more bearable. Additionally, it's easier to clean and sanitize a plastic seat than one that's been improvised from 2 x 4's.
Human feces can carry and foster all manners of pathogens, including e. coli, cryptosporidium, and salmonella. Lacking the ease of care and availability of antibiotics, these and other diseases will be reinvigorated and begin claiming lives.
Keeping a lid on sanitation in your personal RECESS is the first step to protecting yourself and your loved ones from the threat.