Hate to be the bearer of bad news, but you will probably never find an empty Burgertime WITH sideart. An empty game WITH sideart is usually the result of a part out. Some games part out for more than they are worth (vectors, Pacs with bad sideart, and some others), but Burgertime is worth a lot more whole then it is in parts, thus you'll probably never see an empty Burgertime cabinet with sideart.
Its usually no problem to find a painted over one though.