There was a Reaktor .ens that modeled the D50, but roland shut it down... since they've "re-released" (if that's what you want to call it) copyright issues are at play again (so I am told, not that I know anything about them).
www.sf2midi.com to get most of the stuff off hollow sun in soundfont format.....there's some great sounds there....i was never really one for the d50....im gonna get a sy99 if i get the chance coz it has fm and a more complex architecture x
Have you tried Augur yet? It's freeware from Smartelectronics, and you can find a link to it on www.kvraudio.com As soon as you get this plug, go to this URL: http://ann.sounds.free.fr/ Here you'll find the Prophecy Bank, which you can download for free and it's got a lot of those glassy synth/EP sounds you may be looking for. Augur is a freeware emu of a Prophet VS.