Tiny Ups
Waterproof training pant cover which can be used for a little extra protection for EC or potty training. They can be used on their own, or put over underwear or padded training pants when you are ready to make the transition to no diapers.
They are super-cost effective compared to all-in-one waterproof training pants, since you are using the undies that you already have! And they are awesome for EC since they are available in much smaller sizes than most waterproof training pants.
At Wee Potty they are currently available in size M - for approx. 12-20 months or size L - for approx. 16-24 months, but check the sizing chart in the images for more accurate sizing information.
Also note that TinyUps are not very slim...especially size Large. They are somewhat bulky for a reason: they were made to allow room for pairing over Trainers or Undies, and also the bulkiness allows them to be more easily pushed down and pulled up by the child (to aid in independent toileting and dressing).