Post diaperbag to backpack (?) with potty seat help

So our wonderful amazing skip hop forma diaper bag got stolen and I just can't stomach spending another $60-80 on it. I'm thinking its time we just get a backpack or toddler backpack. The problem is this kids potty seat. He's 90% potty trained but absolutely refuses to use a public restroom without his potty seat, so that has to come along everywhere. I'd like to get a backpack that's just big enough. Any suggestions?Here's what we would like to carry - the damned potty seat - at least 1 water bottle - his skip hop snack cup - sunscreen in the summer - 2 sets of spare clothes - wipes case (because he's also scared of normal toilet paper) - a teeny tiny first aid kit with 2 bandaids and a alcohol wipe - my wallet - my 2 phones (because I have to carry my work phone everywhere)I just really don't want to get a giant school back pack. I have a swiss gear one from college that just feels too large. via /r/Parenting http://ift.tt/2vX9foC