I was previously using some plastic rubbermaid sandwich containers, however kitty quickly grew out of it... I tried the ceramic pot method, but couldn't manage to break them properly. Gave her the plastic tray from a cell phone box which I'd serilized, then she out grew that because it wasn't much larger. She was at an akward size where everything was either too big or too small (I'm sure everyone's been there) *and* she's hide fussy.... She ended up taking to some used and sterilized Orange Juice cartons (the size of a 2L milk carton), until I managed to find some silicon bread pans. They are amazing! They're easy to deal with: heavy duty scissors cut through like a dream, simple to clean, they're the odd sort of shape she seems to like and they're durable, and flexible.... If she wants to lay in more of a ball, the silicon just sort of molds around her body.

Plus, they're oven safe (since they're made for baking), so to disinfect you can just chuck them in at 350 for half an hour after cleaning and you're set to go.

Yes, they cost 7$ each, but they look great (chocolate brown), and she seems to love them... At least it got her out of the orange juice cartons!