Inexpensive Source for Cable Guide Clamps

At the bike Coop I've noticed there is many a refurbed bike which hold their cable housing to the frame using zipties. They work, but they're not ideal nor do they look as functionally pleasing; kind of slap-dash. I'm looking for a cheap source of these cable clamps. They don't have to be metal, plastic is just fine and I'm looking for something bolt or slip-on, not adhesive style. Those bikes would be much more appealing if they had a proper housing retainer in place, whether it be on the stays or top/down tubes. There must be some 50cent peice of clip-on plastic out there someplace. I know the Coop would go through a lot of them. If anyone reading this thread (you too Obi-Wan) can direct to a source I'd appreciate it!