Yay for commenters - you've given me some great links! To answer a couple of comments/e-mails, I checked out Walmart.com and Tarzhay.com first, since that's where I used to buy most of the kids' clothes (in person, not on line). They don't have nearly as much on line as they do in the stores, and none of this season's was the right kind of dress.
Kohl's looks good, and Amazon's section could keep me browsing for A LONG TIME.
My favored places for dresses have always been thrift stores (charity shops here) and the last three dresses were actually finds sent over by my mom before she died. So it's a little extra-sad to part with them. I might keep them and make a pillow case for Lily, though.
E-Bay looks very promising indeed - thanks, Elizabeth, for the search tip. I found a couple of lots of the exact sort of dress, going for 20 dollars for three dresses. I think there'll be some bidding happening after payday here.
You all rock - thanks for the good ideas, and now, I promise to get back to regularly scheduled blogging.
Speaking of which, I have not knit in a few days. I've been reading Miss Tey, and the Mystery Socks are currently staring accusingly at me form their spot next to the laptop. Wednesday, guys, I promise!