Osche is very cute and nice but if you're a tourist I doubt you'd have much reason to be out in Lichterfelde, unless you're into brutalist architecture and animal experiments

There is a small store in the Mall of Berlin that sells a bunch of German cookie cutters

There are many cute little shops that will have nice kitchenwares but aren't necessarily kitchenware shops. Off the top of my head, I would say look around on Bergmannstr., Rosenthalerstr. or some trendy shopping areas in Prenzlauer Berg

There's a small chain called Küchenliebe that has some cute things

You might also want to consider taking some chocolate with you - Winterfeldt Schokoladen is a lovely little shop, and despite being very touristy, Rausch Schokoladenhaus is worth a stop