I found what I believe to be a PM set on eBay - it came with a hanger and a plastic burgundy garment bag with a dress picture on it along with the pants, shirt, and navy ribbons. I probably overpaid for it, since the top and bottom buttons are missing, but I've wanted this for Molly for a couple of years now. I could probably fix the buttons.
Buttons aside, I love it. The flannel shirt and corduroy pants have worn well over the years. If anything, the outfit's vintage makes it feel even more like something a real ten year old would wear to play, even now. I didn't have problems with the sleeves, but the waist of the pants were a little snug on Molly. My Molly's a plump PM doll, though - it may not even be an issue with Mattel dolls.
If you can find this used for even a remotely decent price, grab it. It's a great mix-and-match outfit - would probably be wonderful for boy customs, too.