I used Toughtek for the soles - bought my Toughtek from Ahh.biz - no affiliation. I was just pleased with their fast shipping and thought that their price on Toughtek was at least comparable to any others I'd seen. Others have said to watch eBay for the best prices on Toughtek, but I didn't want to wait. :) Because the Toughtek is so thin, I used a layer of Warm & Natural cotton batting between the Toughtek sole and the flannel lining. I think that should be enough - we'll see. I also changed the pattern to have a heel lining - you can see alteration details in my PR review. My only quibble at the moment is that I think the elastic is too long, and maybe that's why Thing 2 can easily take them off. But that can be easily remedied by simply shortening it. Overall, I'm pleased with this pattern and think that it may fit Thing 2's feet better than the Chloe Toes pattern. I will have to make it again in leather for a true comparison.
The outer fabric is thrifted denim from old jeans, and the lining fabric is flannel leftover from one of the toddler bedding sets I sewed before Christmas.