Do you mean a base with free standing glass surround walls? If so, spend a few $ more to buy a quality unit from a plumbing supply house, stay away from the cheap stuff. The finish won't last, the glass is very flimsy, and the extrusions for the frame are thin and weak.
If you mean something to apply to the wall of a built in shower stall, the most ecomical thing that looks respectable IMO is cultured marble. Those DIY multiple piece fiberglass panel kits (check them out at local big box), will forever scream cheap, DIY project.