REST nested resources and resource design

I have a situation where an account belongs_to account_type and
account_type has_many accounts. Obviously, I also have an
AccountTypeController and an AccountController.

I am trying to get a list of all accounts that are of account type
‘user’ without breaking the REST conventions. What is the best way to
achieve this?

I could accept an account_type parameter in the index action of the
AccountController and limit the list by this if it is present.

It also seems like I could go through the the AccountTypeContoller to
achieve this, but I am at a loss for how.

Thank you in advance for your help!