There are lots of VSTs that do about the same thing. In the xoxos VST link posted above, check out Pling. If you want the exact same algorithm in a VST plugin, you could port it to Lua in my scriptable plugin. In fact someone made a nice Karplus-Strong script for it a couple of days ago (I should be merging it instead of making HN comments):
https://github.com/pac-dev/protoplug/pull/8