I brought these Medela nipple shields with my second baby after a week of painful breastfeeding. If I'd known how good they were I would have breastfed my first child for much longer instead of giving up from pain.
The shields come In different sizes to suit and also come with a case which makes them easy to take anywhere.

Medela nipple shields work by being placed onto the nipple just before you start nursing, the baby can latch on and the silicon protects your nipple from getting cracked and sore. The silicon is thin so the baby can still smell the mother and milk. They are then removed and sterilised after use. These are especially good if you already have sore nipples, as I did, as it works as a barrier allowing you to carry on successfully nursing.
I found that sometimes the shield fell off or moved out of place, but most of the time they were excellent.
Baby was fine with the shields, I was worried that the plastic feel would stop him feeding, but it didn't affect nursing one bit, it just meant I was able to carry on feeding and I still am today, he's 12months now!