Where can I find a simple one compartment 40 liter backpack that doesn't make me look like a vegan feminist?

My dad has this pack he got in Germany back in the 70's, its basically a really large jansport bag. Its big enough to take camping and not obnoxious enough to draw attention in the city.

But I just can't find anything like it! Everything is over designed and looks like its made from spaceship material.

Can you help me /out/?