Mason is so tiny and his 12 month stuff is still too big around the waist, he is long and lean too! I bought some Elmo underwear from Target that came in, I think, a 5 or 6 pack and they are SO tiny. The size is 2T but I think they start at 20lbs. So far Mason is still scared of the potty and we are thinking we will have to wait a few months until he is 2 1/2 but I do have underwear when that day comes :) I looked all around and these underwear started at the lowest weight of any that I found. If you are looking for cloth training pants, I was able to find 18 month size at Babies R Us by Gerber. I hope you have some luck!