Hello Ulla! We are also HUGE Tsum Tsum fans. We already have quite the selection. I know that you can get them on the
Disney Store and that the first Tuesday of every month they have a new collection to choose from. This month they have the characters from the new animated film, 'Inside Out'. Next month they will debut the Lilo and Stitch collection. You can also find them at a Target Store near you in the toy section. I have seen them in two nearby Target Stores here in Indiana, but they just mostly have the 'Mickey and Friends' collection. It doesn't hurt to look, though as I'm sure there are different shipments for each Target Store.
As for Disney Parks, right now there is only one place that you can get Tsum Tsums and that is Once Upon A Toy in Downtown Disney. I was just there last week and the shelves had the most variety that I had seen anywhere. As of last week they had the entire Big Hero Six collection, the Frozen collection, along with Mickey, Minnie, Duffy, Dumbo, Stitch, Chip and Dale. I just had to buy Hiro and Baymax for my son.
If you need anything else, please come back and see us! Happy shopping, and have a magical Walt Disney World vacation!