It is not limited to 5 L jugs. You can use any compatible water container that the suction tube fits into, provided the container can be sealed properly and is suitable for the pump's connection.
Yes, please refer to the products in the link below.
https://eur.vevor.com/beer-pump-c_10707/water-bottle-pump-system-1-gal-min-40-psi-water-dispenser-pump-with-20ft-pe-pipe-p_010656141135