Actually, the packs do work on both EU and NA versions of the game, but obviously, that only applies to the UMD version. If you make an EU account and get funds into it (I guess you'd have to get EU PSN cards from ebay or something, unless Paypal works for other region PS Stores), you can use the packs on your PSP. You could do that on your Vita too, but you'd have to buy the game again on the EU PS Store.