Diaper bag for when babywearing

centralperk

I wasn't sure where I should post this but what diaper bag do you use when your babywearing. I take mainly public transportation and don't always want to bring my stroller. I have an ergo currently along with a moby.

Backpack? messenger bag? I tried googling it and came up with some answers but would love to see/hear what others use that work really well for them. 

freezorburn

Ergo makes a backpack style diaper bag that can also velcro onto your Ergo. I like it so much it has become my all-the-time diaper bag.