I don't consider it a fanny pack but I have Mountainsmith Lumbar Day Pack. Amazing piece of equipment as long as the strappettes are used to carry it like a pack.

Some might consider it nerdy or such, but when I am outside of my house you can almost guarantee I have a ruck on my back, anything from my goruck GR1 to a REI Flash. I went into a Safeway today in workout shorts and slung a mesh drawstring pack I got at a race expo for free.

I think if your comfortable and confident, you can pull anything off, even a fanny pack.