I have two spare remote FOBs for my 2001. I think they are used up till 2003 but better check yours to be sure. FCC ID number on back is KPU41701. $35 per remote. We can program it when you come to pick it up (plus makes sure it works for your car).
Currently Miata-less... 2007 Brilliant Black NC PRHT, to replace 2006 Winning Blue NC, to replace 2002 SE, to replace 1993 LE #1322 and so on and so on...