These pastel erasers from the Japanese brand, Kokuyo, are perfect for you to keep with you on the go in your pencil case.
The thin pen shape body means that it will easily fit inside your pencil case without taking up too much space, and the push up slider allows you to retract the eraser so that it doesn't get damaged or cause a mess.
The rubber is soft and quite durable (meaning it shouldn't break too easily), there's even a refill included in each box.
There are 4 colours to choose from, white, yellow, orange or blue.