Just respray the damn thing with white car paint and a good spray varnish. Replacing the keys would be a good idea too. Oh, but wait. Once you've paid out the extra for paint and varnish, the keys, and/or retrobrite and sealant, or whatever you choose to use, you could probably have just gone and picked up a better condition A500 in the first place. Could be a good bargain for someone local if they only pay the minimum bid and pick up in person though, I doubt if it's going to get a lot of bidders.