I second this @Uno

As it stands- you have the inventory of the "Shopping Bag" set to be a 6x14. Which- as you said is "Not very convenient for adventurers" - Thats cool and all. But as someone who wants to sell weapons- it is extremely inconvenient. Think you could make a second 10x10 version that doesn't stack items? So one is for food and one is for weapons kind of thing? (So you can make whichever for whatever shop you are trying to make without being forced away from the mod that is solving the issue of selling backpacks being ugly?)
Could increase fabric cost for the 2nd type to compensate or something- change the icon to be darker so you can tell them apart and such.