There is a display case object in the A.C.E. combination library. You can get that here, donation suggested:
http://www.archicad.ca/?page_id=6
Andy has combined a number of localized AC libraries as well as custom parts from some of the best GDL's around. However, be warned the library is very large.
Erich
AC 19 6006 & AC 20
Mac OS 10.11.5
15" Retina MacBook Pro 2.6
27" iMac Retina 5K