She wears wigs size 3-4" (this one is a GLiB mohair wig from mudoll.com)
Tops same size as Puki Puki
Pants for Pukis are a wee bit too long (and wide) for Momo, but depending on the style and fabric she can still wear them. The ones she's wearing in this pic are actually tight fitted leggings. I reckon Lati White pants would be a better fit (just make sure they aren't too slim).
Shoes same size as all the other tinies; Kelly/Shelley (Mattel) is a good choice. These UGGs are handmade by Mimi's stuff, there are a few others who also make these and Mary Janes (Willow's Wardrobe, Spampy's stuff).