>>503461I bought one of these like a year ago and it's holding up great
ebay.com/itm/Military-Tactical-Backpack-Hiking-Camping-daypack-Outdoor-shoulder-Bag-50L-USA-It seems to be made by a korean company, it had a bunch of copyright infringing promotional material and names on it but it's build quality is totally legit. It might not be clear from the pictures but the backpack straps can go into a zip up compartment and you can then carry it like a duffle bag (long shoulder strap) or suitcase/daybag (short handle)