Your best bet is Benkler Elektronik. Good quality cases with good prices. I use them for all my projects and know of others who use them too.
You can get different frontpanels although i believe no 5mm, only 3mm or 4mm. I use 4mm and never had a problem with stability.
It's already in the meta thread but the address speakon.de now belongs to neutrik. Go to:
http://www.robeshop.de/
Flo