I have a Think Tank "Urban Disguise" bag that's more of a "man bag" than camera bag in appearance (the maker's intent, no doubt). I have the 30 size which is pretty much suited for one 35mm, a spare lens, a handful of film and maybe a flash; the lens can be fairly long. They make it in several different sizes. The bags seem well made, but the zipper opening across the center of the top, as opposed to a flap, makes it tedious to get stuff in and out.
Like Rick A, I also have a couple of non camera bags, indeed one from Cabela's. But after 70 years and many tries, I still haven't found the "right" bag! (Maybe it's because I keep doing different projects with different equipment - nah, that couldn't possibly be it! )
These days, a non-camera bag might be perceived to contain a fancy phone or tablet computer, so maybe those diaper bag ideas are best!