# admin.py

# The list of objects can get extremely long. This method will 
# override the filter-method for objects by specifying an extra
# attribute on the list of choices, thus only displaying a filter
# method to those objects actually existing in the database.
class CustomChoiceFilterSpec(ChoicesFilterSpec):
    def __init__(self, f, request, params, model, model_admin):
        super(CustomChoiceFilterSpec, self).__init__(f, request, params, model, model_admin)
        self.lookup_kwarg = '%s__id__exact' % f.name # Change this to match the search of your object
        self.lookup_val = request.GET.get(self.lookup_kwarg, None)
        self.objects = model.objects.all()

    def choices(self, cl):
        yield {'selected': self.lookup_val is None,
               'query_string': cl.get_query_string({}, [self.lookup_kwarg]),
               'display': _('All')}

        # Filter the call - change i.item to whatever you are filtering on
        items = [i.item for i in self.objects]

        for k in items:
            yield {'selected': smart_unicode(k) == self.lookup_val,
                    'query_string': cl.get_query_string({self.lookup_kwarg: k.id}), # Change .id to match what you are searching for
                    'display': k}

FilterSpec.filter_specs.insert(0, (lambda f: getattr(f, 'compact_filter', False), CustomChoiceFilterSpec))

# models.py
# This is just an example
origin = models.CharField(max_length=2, choices=COUNTRIES, verbose_name='Country of origin')

# Add this to the item
origin.compact_filter = True