Those are cute! Thanks for the link, I wasn't quite getting the idea of flip flops for babies. Congratulations on the grandbabies on the way!
A quick search at ravelry.com for sandals (flip flops for babies came up nothing) got this: http://www.ravelry.com/patterns/sear...ort=popularity
I don't know if any of them are what you want. Not to say you should crochet them, but if you do crochet you might want to try them crocheted. The crochet patterns seem to be easier to find.