I think you could probably find these costumes just by searching around through stores and places like Goodwill and Salvation Army. I don't think green blazers are too common, so that would be more difficult. You could find white blazers and dye them green (I suggest RIT dye), and you could use bias tape for the lighter green/yellow green bits.
Current Project: Hikaru Shidou ~CLAMP in 3D Land~ (Magic Knight Rayearth)
2014: Genericon, PAX East, Otakon