If a scan is enough you can found a lot of covers here [http://kofperfect.hypermart.net/] or here [http://www.vgmuseum.com/scans/neogeo.html]. I asked nearly the same question at the neo-geo 16bit forum
Cool! Thanks for the info on those sites that is definitely a step in the right direction now that I know where we can find most inserts where can somebody get an actual case? to put the insert in?