You don’t necessarily need a VPN (virtual private network), but it is likely to be useful, not just for this, but also to e.g. use Sky Go when travelling, etc. I find SaferVPN very reliable and good value. Once you have installed it, choose a USA identity, and then log on to the site from which you wish to download.
Set up an account with the download site, using a valid US address and telephone number. Then buy your download, and specify PayPal as payment mechanism (you will need to set up a PayPal account first), and then proceed to download.
It is nearly 4 years since I set this up first, so I don’t know if it will still work, but it’s worth a try. There’s nothing so frustrating as knowing that there is a 24 bit version of something you want, and not being able to buy it.