I have the same problem OP. Need to carry water, laptop, headphones, papers, two mob phones, lunch and fruit, umbrella…it adds up. I use a pale backpack in summer, it’s ugly but needs must! 9 months of year, after about six previous work bags I now use a leather flap tote bag (Ferragamo, bought third or fourth hand!). What makes this work is that it has a single shorter wide handle, so it sits on my shoulder and tucks under my arm, or slings onto back to make carrying its weight a lot easier. I have 20 min walk after train to office. It is seriously my holy grail workbag, if it breaks I will have it hand remade for me😃. That shorter single fat handle has been a game changer! I would look for a pre loved item and spend the John Lewis on something else (do they still sell vintage jewellery?)