Going over you inventory weight allowance is a bit of a pain. I don't suggest getting rid of item weights (that would be too unbalancing) but I do think that 'weight mitigating' items could be available.
Real containers (I don't think there are any now, are there?) would be rather code heavy so I was thinking of 'pseudo-containers' with a weight-mitigating factor that cancels out some, or all of the
inventory weight. Rather like having a 'negative weight'. (NOT cancelling weight of equipped items). To avoid exploitation it would probably be best to allow only one such pseudo-container to be used at a time.
Non-magical containers could be bought in the General Store.
Coinbelt (-2kg) 30 gold
Handbag (-3kg) 50 gold
Belt Pouch (-4kg) 60 gold
Shoulder bag (-10kg) 120 gold
Backpack (-20kg) 200 gold
Magic containers could be found in the magic shop, black market and/or dropped in dungeons. I suggest making relatively rare and expensive.
Magic bag (-40kg) 2000 gold
Bag of holding (-60kg) 5000 gold
Obviously actual figures would be adjusted based on gameplay experience.