You can get them everywhere online. I haven't seen many in stores. And you can get them in varying sizes. When I did Low Carb many years ago they were big and there was a place everyone got them from at the time. But again I am pretty sure that was online. The small ones hold 1/4 of a block and the slightly larger ones a 1/2 block. I think eBay was good too. Start around $20 all the way up to $100 from memory. I'll search through my emails and see if I can find out. Or maybe tan can PM you what she found.

Google Butter Bell Crock. That was the one everyone had. There are Aussie stockists too.