PBparts.com usually has a decent selection of case plastics, however they aren't cheap. Your best bet is to keep watching eBay for a 700MHZ G3 ibook or lower if you want to strip the paint and make your own design. Get one with a dead screen then part out the other electronics. After that and into the G4 line Apple moved away from the painted lexan. To some degree you might be able to use different model case plastics, but it will probably require extra work. Tho' I vaguly recall someone using newer parts in older plastics.