I just got a PM about what I use
http://www.ebay.com/itm/232176370930?_trksid=p2057872.m2749.l2649&var=531384982329&ssPageName=STRK%3...I chose the 3mm thick reinforced fiberglass sheet. It is black, good looking, very strong and easy to work with. I soften sharp corners. Way stronger than plastic.
A small flat file is useful for making square holes and a rat tail file can enlarge a 3/8" drill hole to 15/16" for toggle switches.
A friend with a table saw can cut the 8-1/2" x 11" sheets so as to make a cupola or three side box with front drop for screws or adhesives.
Superglue seems to work excellently bonding sheet to sheet. Goop for adhering to metal - or perhaps pop rivets with pop rivet washers.
Auto Stereo equipment suppliers such as PARTS EXPRESS sell very inexpensive decorative fasteners and bezels, if that's what you wish.
