I'm not trying to attack, but honestly I'm struggling to understand what you're looking for?
Are you talking like handbags and purses? OR do you mean backpacks?
Most handbag/purse type carry accessories are universal. Some are larger to fit larger frame handguns, but for the most part they are all universal holsters. As for the open carry part? I'm really bumfuzzled here. Why would you open carry a handgun on the outside of a bag that wasn't securely attached to you? How could you possibly draw effectively from a bag like that? Unless you have something specific in mind? Just my thoughts, but that seems like a cherry to be picked off in a gun grab.