I'm sure some of you may have heard about this, but as far as I'm aware nobody has ever tried it on a yellow bubble. Have a read of this:
http://stiggyblog.wordpress.com/2011/09/11/nintendo-gameboy-gets-the-retrobrite-treatment/
As you can see, this product readily available from Boots reverses the yellowing of old games consoles. I wonder whether it would have the same effect on a bubble? It can't be that hard to get it all over the bubble without damaging the card.
http://stiggyblog.wordpress.com/2011/09/11/nintendo-gameboy-gets-the-retrobrite-treatment/
As you can see, this product readily available from Boots reverses the yellowing of old games consoles. I wonder whether it would have the same effect on a bubble? It can't be that hard to get it all over the bubble without damaging the card.