Walmart online carries Shield fabric(a type of PUL fabric that they use for diaper covers)-knit on one side and waterproof on the other. I just ordered the 12 yd roll for $47. Else where it is so much more. I use it for bibs, changing pads etc and just add it in the middle. They also have a small one yard craft size for $9.
https://www.walmart.com/ip/Shield-Li...-Bolt/51620133