This is actually a frowned upon practice among arcade collectors because they would rather see the hardware used to restore cabs, not improve Nes systems, so its not too likely if you say that is your plan you will get much in the way of help. Honestly anyway you should be hitting ebay or calling up local vendors in your area and looking to see if they may have dead pcbs around somewhere they might part with. Ebay wise it will take some time, they pop up here and there,you just have to keep a eye out. You can try the Klov forums too, and see if that gets you anywhere.
Also, my understanding is you can infact use the Choice 10 PPU. Here's a trouble shoot type thread to help you out on the mod. http://nfggames.com/forum2/index.php?topic=1592
Yeah that's why I stated it was preferable to have the already gutted chips rather than an entire working pcb. I am also confused as to what exact boards have the chip: the RP2C03B, If I had a list it would be helpful.
On a side note: I know many frown upon the gutting of chips from arcade pcbs for other purposes than restoring arcade hardware, but there are many others who don't. Besides once I have the hardware in my hands I have the right to completely destroy it if I so wished. (though I understand if someone knew this my likelihood of getting someone to sell me one would be much lower)
I understand the frustration of losing working hardware or anything else for that matter for something that isn't being produced any more, nor has been produced in years. But let's face the facts: everything will eventually die or stop functioning, why not use the hardware for the time being for something that I value more?
It may vary from person to person what they value, for example say hypothetically that the phillip's cd-i just happened to have a custom chip that could be used to restore or enhance a more popular, yet expensive/rarer system like the pce hardware. That is assuming there was a lot less pce hardware in existence. Also assume the cd-i is still very hated and the pce was still very loved. If you were one of the ones who values a pce over a cd-i, would you not gut the system's ship for use in the pce hardware? I am also sure not too many would mourn the loss of a phillips cd-i except for the few who liked it.
Btw I'm not arguing with you, just putting out my two cents on the subject, I appreciate the tip, as I didn't think of it that way when I first made this post.