You'll find that one in the FS section on here as wellSnaketibe said:Sadly there are indeed some yellow SW bubbles as well. Most seem to still be clear, but I've seen several Palitoy 12 backs with yellowed bubbles, including some graded as yellow for what little that's worth!
Edit - Just found this: http://www.ebay.co.uk/itm/STAR-WARS-PALITOY-12-BACK-DEATH-SQUAD-COMMANDER-UNPUNCHED-ACTION-FIGURE-AFA-UKG-/172294932592?hash=item281d940870:g:guEAAOSwbsBXo575