Unable to Buy the Final Season of a Series Separately

I want to buy season 3 of Miss Fisher’s Murder Mysteries, but it’s only available to buy in a set with the other seasons, however, I’ve already bought the other two seasons separately so would like to avoid having to re-buy seasons. Season 1 & 2 are available to buy separately, it’s only season 3 that is a problem. Is there any way to get around this?