Don't know if it varied from year to year, but I ordered one from Xterraparts to have in my spares kit and it looked like a regular relay (little bigger than 1" or so square) but it was blue. Since it was to be a spare, I never crawled in there to see if it (visually) was an exact match.
You may want to consider going online to the Nissan Web site, pay for a one-day subscription to get access to the service manual for your year and download the info. The chapters save as pdf files and will have the info you need to work on your X. That will tell you exactly where to look.
Hope this helps.