Who makes a 1"OD SST Idler for .5 wire rope/cable

Unless you live at the top of a remote mountain, you should have access to suppliers such as McMaster-Carr etc.

If it were me, and I only required a few, I would grab some delrin round stock off of my shelf and throw it in the lathe.

Look for industrial suplliers on the web

Here's a good link:

http://power-transmission.globalspec.com/SpecSearch/Suppliers/Mechanical_Components/Power_Transmission/Idler_Pulleys?SrchItem=1