You can get other spoilers. The best other one that I found was this one on a Micra on this site. Two problems with that - you have to get it from Japan and you will have to talk to AMY or Solarice on this forum because they can get you one in.
Nismo Micra Spoiler (Japan) -
Body Kit - There aren't many good body kits for the Micra from the UK. As the car is japanease, all the good body kits are made over there and therefore you will also have to get someone to import them for you. This may be a little bit pricey because of the importing fees (P&P).
An example would be the Wald Kit (2 pictures below) -
Your best bet is to look around and talk to different people and see if they can get you anything. Hope this helps and give me a 'thanks' below my comment if you think that this was useful to you. (Y)