Being the conciousness of Elder Gods lends one some strange powers.

The only other all-plastic alternative I can think of is scratch building your own. This sounds about 100X harder than it actualy is (ie: it is really, really easy to do). Cheap "tread plate" or "diamond plate" can be had through Plastruct and (probably) Evergreen, amongst others. They also have all sorts of industrial shapes (ie: I-beams, L-beams, H-beams, etc..) in various scales and in some form of extruded styrene.The last bit is some clippings of the sprues you (should) already have laying around from older kits and and spare gubbins and so forth.
Here's some
WIP urban rubble bases I did for a unit of Grey Knights (that I've stalled on). All the bases need is a bit of sand and they're done:



All were really easy to do. In a single evening one could easily knock out 20-30 (or even more) such bases. Fun to build too.