I got to make something very clear quite a bit of PSP DLC is still available through PSN. It's just the way you have to get it is I admit a bit crazy. First of all, you have to get a PS3 if you don't already own one. Like I said it is crazy but it does work, I know I have done this. Next, go to the PlayStation Store on said PS3. I found their menu quite easy and I was able to find like I said PSP DLC, and as it was when the PSP servers were still Online about half of it is FREE. Including that patch for LittleBigPlanet PSP which I have been told makes the game more playable. Once you downloaded it to the PS3 HDD. Use your USB cable and connect it to your PSP. Then use the menu to copy it over the instructions are simple...but you must be online to do this.
I promise this does work.