How allow access to single account register?

I'm trying to customize a role for an accounting clerk who needs to be able to add transactions and reconcile a single bank account. It would appear within the roles that the only way of doing this would give this person access to every bank account or none. I found in the account set up that you can restrict the account to a department - which would require me to create a new department just for this person and then figure out how to make sure it is also accessible to others who need it who may have expanded access.