There is not an aftermarket market for CDIs (not kaw anyway) that I know of. Buying one used is an option, but you won't know if it works until you bolt it on your bike.
You might try the 'For Sale/wanted' forum on this board.
Some have dug the potting out of the box and repaired them. The most common failure is the SCR. No. I don't know what SCR your CDI uses. Repairing a CDI isn't something you will likely accomplish with average mechanical knowledge and common hand tools.
Good luck!