Hi,
since GM has this no longer in stock, the only chance is fleebay, scrapyard and so on.
Ask Greg (gregster) - he some years ago offered an exchange by sending a repaired one and the broken on got back to him. Don't know if this is still possible.
I once had a spare from aftermarket - someone over here in Germany made a little series. But I was not lucky with it because the breather was not working and oil was pressed out. However, I only recommend an original spare or a repaired one.
Someone suggested an adapter-ring to use a cover from a Jeep. But I have not followed this closer.
Good luck!
Kind regards,
Ian
Sorry for my pigeonenglish.
My doctor says I have to invest time in SPORT