Pinball Resource are now offering playfield inserts individually in most sizes, including 1inch but sadly did not see a yellow one listed the page.
But I just went and checked the bag of mixed inserts i got from them not long ago and there was 2 yellow 1 inch inserts, so if you want me to bung one in the post for you PM me your address.
Here is the PBR page.
http://www.pbresource.com/playfins.html#1Chris
