Leather/ canvas edc duffle bag

I am looking for an edc bag that is made out of traditional materials like leather or oiled canvas. When I'm at work I am not allowed to be on my back it can only be on one shoulder like a duffle bag, but when I'm in the woods I would like it to be work like a backpack. It needs to be able to carry lunch, gym clothes things like that. I'm looking for a sturdy bag that's not ridiculously expensive. Thank you