I can’t add to the bathroom business, I’ve never had to go while in the middle of a run.
But for hydration, I decided to buy
this unit from amazon a couple of months ago when I was doing several climbs up camelback mountain in Phoenix and starting on some longer (for me) runs. It doesn’t hold a ton of water, but it’s enough and it is comfortable to run with...no significant bouncing. It also holds my phone and wallet, and I figured out how to get it to hold a small water bottle or two as well if needed extra water.
I’m happy with it, seems well made and does what I need.
You could probably hook a roll of TP onto it as well if you needed to.