Your profile doesn’t say where on the humongous continent of Australia you are located. I know that @skeggley has asked about them, and been told that “salted rats” are not available in Australia.
However, I think another forumite has made or found one somehow, I just can’t remember who it was. Somebody like @busso could perhaps be persuaded to make one for you. Also @Peter48 would perhaps suggest that you contact a local “men’s shed” if you have one. Given the dimensions, they could very likely make one for you.