Wolfgang Palm, the maker of the legendary PPG Wave synthesizer, gives Plex 2 away for free via the website of Hermann Seib. The plug-in is available for Windows.
A few years ago this interesting VST synthesizer was a commercial plug-in sold by Steinberg, the manufacturer of Cubase. Plex 2 is a very special synthesizer that you will not immediately understand if you are used to conventional synthesizers. The synthesizer does make interesting sounds. It is certainly recommended to read the (not quite up to date) user manual.
Unfortunately, the site of Hermann Seib has not a great bandwidth. But there are some generous synthesizer enthusiasts who have created a mirror site with much higher download speeds. The mirror sites can be found in this thread on KVR.