OH MAN! i sold it years ago...but i used to have a one off HSGI "bowling ball bag" . It was awesome, molle webbing inside and out, pockets and beefy grab handles, YKK zips. It would be perfect for your poop makers needs. Think i sold it to a soldier , who used it for his chopper helmet.
I used the maxped versipack for a while when we had our first. Small, but you can fit a lot in there. If i still had it I'd give it to you.
The SOG ninja backpack makes a great diaper bag. https://www.amazon.com/dp/B0131SE0KI?psc=1 Not expensive, lots of pockets , a bottle pocket for, well, a bottle. OD green, not multicam. It's a cheap version of a 5.11 rush 12. I have one in my truck (former diaper bag) as a just in case I want to go wander in the woods pack. It's actually a good little pack for the money.
This is the bag I use for the kiddo... AMAZING quality. Even my wife loves it. https://www.missioncritical.cc/products/messengerdiaperbag
