just look under "stone-natural" in the yellow pages and you should get a bunch of hits.This is where local contractors would go for their stone counters,vanity tops,decorative bases,whatever.
many will have a showroom with samples and do not have a minimum purchase plus they will for a small fee cut the stone to size for you-a real help for doing either amp bases or equipment rack shelves.
the Corian does not have the mass of natural stone but is far easier to work with and even a skil saw is OK.It can be routed,shaped and sanded
Pretty much anything you can do with a piece of solid wood you can do with Corian and except for the weight would be hard to tell from the real thing,that is why it is so popular for kitchen counter tops.The "look" and color varieties
Another option worth considering is a local garden center,even better if it is one that caters to landscapers and Koi pond builders.You can find many instances of pre-cut decorative stone materials that only will need for you to add feet and seal/polish the stone.
anywhere contractors buy goods,even the home depot garden center and cabinet shop will have maybe that one special thing you need to inspire for a project.
good luck with the inspiration man