I used AC Ryan MeshxPanel™ HEXX 500x500mm Alu Black (XP00618) from www.specialtech.co.uk You should be able to source something similar from any PC store. 1 sheet did 2 holes so you'll need 2 sheets for all 3.
First, in case you don't have it, here's the basics for taking the bumper off..
"1. Put the front up on axle stands.
2. Open the luggage lid and remove the black plastic cover around the latch. Use a big bladed screwdriver and turn the buttons 90 degrees to release.
3. Remove the 2 philips screws and cups underneath that secure the PU.
4. Remove the buttons that secure the front section of the wheel arch liners. BTW, taking the wheels off helps access but is not essential.
5. Crawl under the car and remove the row of philips screws and buttons securing the bottom edge of the PU.
6. Pop out the indicators by pulling the rear edge outwards and then sliding them rearwards. Remove the exposed screw underneath. You will also see the pointy end of another screw on the bottom edge.
7. Removing the bottom PU screws will have slackened off the wheel arch liner so tug it loose so you can get your hand and a screwdriver inside the PU, under the indicator position and feel for the last screw.
8. Put a dustsheet or similar on the ground and ease the PU forward. you will have to spread the sides a bit to get around the indicator moulding.
9. Have a beer and inspect the wildlife in your rads."

Once off lay the PU on a dust sheet or similar face down, carefull of scratches. Cut the mesh roughly into shape leaving a couple of inches all the way around, this will allow you to mold and fix. I used a 2 part epoxy resin to fix but others have used a hot glue gun. Apparently the GT3 bumper has grub screws around the holes which you can use. Just take your time getting the mesh to line up and let the glue cure fully. Then just follow the reverse of taking the bumper off.
Have a look at www.carnewal.com for the actual prefabricated grills.

 

WOW! great info, I appreciate you taking the time to post that not just for me, but for everyone who was interested in this thread. I think this information will help all of us, I'll let you know when i'm at the step where I get to enjoy a New Castle beer. Thanks again Dervish.

 

No problem, I got the info from a few sources so it's just a case of passing the knowledge on...

 

You should call Brian at www.afterhoursautomotive.com - he has the really nice race car stainless weave mesh. He did the mesh install on my 996 GT3 bumper openings, and also a custom block plate for under the top bumper RS openings. You may actually want to block off the front opening to pavement... I don't know how it will affect aerodynamics by having air pumped in the front and directly under the car. Might want to let Brian take a look at it since he is a genius with these types of solutions. Tell him Kurt referred you. He's located in Wilmington / San Pedro area. Really nice guy.

 

one more thing- the stainless square weave mesh is bad-azz because it does not bend or dent if hit with rocks (like stamped metal mesh does). The weave "gives" and is made from a springy type of stainless wire. You could kick it with your foot full force and it would break away from the car before it dents.

 

Thanks Kurt....you guys are awesome, all of you, more helpful than any Porsche dealer in So Cal....I will look into getting a hold of Brian.

 

where are the pics?!!

 

Ah yes, the pics, well the body shop is taking their sweet time putting the bumper back on....i guess the black Toyota Solara with a busted headlight being paid for by the insurance company got priority over me (a cash paying customer who has given this body shop more business than the Solara owner ever will, time to call and jerk their chain a bit). I should have some up by tomorrow or wed at the latest.

 

I think the bumper looks fine as is!