I have seen books at Meijer )I think) and Walmart. My parents found a Molly bath tub doll that the hair changes color a little in the tub and my brother got my daughter a Molly doll from Amazon (watch the prices though. THere was some major price gouging earlier - he only paid about $13, but some people were charging $50!). He siad they had Bubbl ePuppy and one other character, too I think.
If you go to the Nick Jr. site there are some patterns for Molly, Gill and Bubble Puppy. Also some other craft ideas.
There is some toy that looked really boring and got bad reviews. It looked like a funhouse at a fair. It also said you could buy other characters for it, but we could never find them available.
I am hoping they come out with more stuff, too!