Not as far as I know. They currently have a beta tester program where skilled trainers can apply for one and it is created to order. There is also an adoption program. Those Type: Nulls have been... neutralised for battle as they put it, so anyone can apply for one. They say the Nulls they adopt out are ones who have lost their owners or were returned for some reason.

[Does Armin entirely trust this? No. No he doesn't.]