PioneerGuy75
Certified Lurker
When I was in graduate school the shop in our department used methylene chloride to build Plexiglass apparatus for polyacrylamide gel electrophoresis (basically we're talking about a Plexiglass box). It works almost instantly, bonds water-tight (the box was filled with water-based buffers for use) and does not "craze" the Plexiglass.
I don't think methylene chloride is all that readily available anymore, though.
+1
My family used to be in the sign business and always used methylene choride to glue plastic letters to plexiglass
Good luck!