Cheapest single sim plan with 40GB+ data

Been abusing the Kogan $5 for 40gb for as long as I could with my dual sim phone with a long term Amaysim as my main number but now I got the super cheap Galaxy S21 which only has 1 sim what would be the best sim plan with atleast 40GB? Im looking for something long term, 6 months+ then I could port if needed.

Thanks