To answer the first question, I think several people decided to start calling it the N20 or Nacra 20 because there is a Monohull out there called the I20. I found it a couple times searching for tuning specs.

New tramps should not be too hard to come by, The sail maker here in Greenville makes them for any application as long as he has a pattern (your old tramp). You should not have too much trouble finding someone there to make one. It should be considerably cheaper than a Nacra one as well.