A piece of natural crepe,like Nightwolf was speaking about,makes a great glue eraser.Most cobblers I think would be able to help someone out with a piece,I've always got some kicking around.
I would try and find out what the buyer wants to sell them at and charge 1/3 to 1/2 of the price,probably 1/2.If he knew how to do it he probably wouldn't be asking.