Associate parameterized fixture with parameterized test in pytest

I want to do something similar to this in pytest (this is just a simplified example):

import pytest

@pytest.fixture(params=['A', 'B'])
def fixture1(request):
    return request.param.lower()

@pytest.mark.parametrize("extra_arg1", ["1", "2"])
def test_xxx(fixture1, extra_arg1):
    assert fixture1 + extra_arg1 == ..... 
    # the test is expected to run 4 times and the results should be "a1", "b1", "a2", "b2"

How can I associate the parameterized fixture with the parameters in the test? Note: I have to use fixture because it has been already in place in the project repo.

Thank you!