↑ It got me thinking whether creating a US Account would do the trick. I've had this game before that had some free DLCs up for grabs. Trouble was, my local game retailer gave me the US Version of the game so I was forced to go and set up a US Account for myself just to be able to download them. Maybe creating a US Account would give you access to the US PSN Store and you could buy it then?
I'm not really sure if it would cause problems for the actual transaction though, I haven't really bought anything off of PSN (or done anything with my US Account).
You can if you want to, I have a JPN PSN account and no problems so far.