Honestly your chances of finding a complete cold air kit for your WD21 are very slim. You most likely won't even be able to find a decent modular cold air system, they just don't exist for this vehicle. Most performance companies probably discontinued any production items for the WD21 with the release of the R51 (or maybe even long before).
I would probably say that a pop charger would be your best option. The only pop charger that I could find which would be compatible with your WD21 is from Stillen. It looks like it's high quality, but it's a bit on the expensive side. The kit will run you $185 and it isn't 50 state legal yet. I'm sure you could find other pop chargers for your WD21 if you do a thorough search, this is what I found after about five minutes of searching.
Stillen High Flow Intake Kit
http://www.stillen.com/product...HFIND