Do you have a model for both Suppliers and for Users? I'm having a hard time understanding your question, but you should be able to do something like this.

User Model:

class User extends Eloquent {

    protected $table = 'users';
    protected $primaryKey = 'userid';

}

Supplier Model

class Supplier extends Eloquent {

    protected $table = 'suppliers';
    protected $primaryKey = 'supplierid';

}

Then you will be able to use Model::find($id) or Model::findOrFail($id) to accomplish what you are doing. If you want to return specific columns, just end your method with

->lists('column1', 'column2');

If I am understanding your question correctly, that should do what you need it to.