http://imagej.273.s1.nabble.com/Adjustable-Watershed-in-Fiji-tp5012868p5012874.html
It was compiled with plain ImageJ; does it work with Fiji? Don't forget that it needs uppercase first characters; by default it will be all-lowercase when downloaded.
If it works like this with Fiji (I am still using plain ImageJ) I could add class files also for other plugins.