I didn't think you need a new passenger side airbag cover. I thought it was just a door on a hinge. I think the airbag is a separate unit that can be replaced using the old cover. You just have to take out 2 bolts up under the dash. The whole thing (airbag & cover) will come out towards the seats. There is a pin that holds the cover on the the rest of the airbag assembly. Slide the pin out and remove the cover. Get a new airbag, slide pin back thru cover and put it back into the dash.
http://www.ebay.com/itm/2000-BOXSTER-S-986-Porsche-R-Dash-AIR-BAG-right-passenger-64-895-/301046498105?vxp=mtr&hash=item4617c50339