Styrene with Patterns (e.g. not plain sheets)

Where can you find styrene with patterns such as squares or rivets like dots?  All that seems to be available are plain sheets in various thickness.  My problem may be because I don't know what they are called.  At Evergreen they have various names but no descriptions or pictures so I don't really know what they mean when they say "Clapboard" or "Novelty".

Thanks!