I found a place in Langley, BC that claimed they could make anything...and had acrylic up to 1" thick. Unfortunately, they had no experience making aquariums in particular - which made me nervous.
In the end, I went with Envision in Oregon.
http://www.envisionacrylics.com/index.html
He provided a lot of experience and actually built things into the tank that I had not considered. (ie. removable overflow strainers)
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400 gal reef. Established April, 2007. 3 Sequence Dart, RM12-4 skimmer, 2 x OM4Ways, Yellow Tang, Maroon Clown (pair), Blonde Naso Tang, Vlamingi Tang, Foxface Rabbit, Unicorn Tang, 2 Pakistani Butterflies and a few coral gobies
My Tank:
http://www.canreef.com/vbulletin/showthread.php?t=28436