There are many reasons you may choose to supplement breastfeeding, whether with pumped milk or formula. If you are looking for a method that least disrupts the breastfeeding relationship, the tube at-breast is a great option. It allows you to continue to bring baby to the breast, working on latch as well as bonding.
I like this system because the container is a bottle, which feels less medical than a bag or container suspended above baby. It is also a reputable brand and high-quality materials.