Hi, you should only use the Kohler condenser and the original Kohler part. There's probably some condensers that are the same, but there's no good way to know for sure. Also, never use automotive condensers. I also don't use the aftermarket condensers, even though some are just as good, or even the same part as the Kohler.
The primary reason is for point life. The wrong condenser will ruin the points and could possibly damage the battery in a battery system.
I've worked on a lot of K-series Kohlers and own a few, great engines.