As I mentioned in IRC a little earlier, if anyone is really stuck with getting an unpatched GTA, PM me.
I will downgrade your PSP for you, if you're prepared to pay postage both ways (I live in the UK) and a small donation for the time taken.
If I brick your PSP, I will replace it, but you will need to supply proof that it is currently working to avoid abuse.
Perhaps people in other countries would be prepared to do the same. If so, add your name and country here.