It's pretty low-tech. First, find some suitable screening material (metal). If it's not silver, I'd recommend you get a can of spray paint and "silverize" it. That way it hides what's behind it better. Black tends to be less visible, and then you can see the screen sorta and what's behind it...and it looks too busy/messy for my tastes.
So use whatever you can find. I couldn't find too much so I ended up going with some aluminum stuff that's supposed to cover your roof gutters to prevent leaves and crap from blocking the water flow. You should be able to find that stuff in any harware store (I got mine at Canadian Tire) in the gutter/eavestroughing(sp?)/downspout section. Unfortunatly, this stuff is not wide enough to do the job in one piece.
The stuff I got was appx 5 inches wide or so. It also has a curve to it, which I decided to leave for the most part, I straightened it a bit though. I measured the lenght and snipped the material to fit. So I put one 5" piece on the right side of the rad...the other 5" piece on the left side, and was left with a gap of an inch or so down the centre. So I cut a 1 inch piece and connected them all together. I just used some wire to twist-tie the links together basically. Make sure there are no sharp peices sticking out anywhere that could peirce the rad.
Then I just fit it in place with some duct-tape while I bent it a bit here and there and worked on the permanent mounting. I mounted it in 6 places, the 4 corners and centre top & bottom. Again, I just used some fairly hefty, yet bend-able, wire to loop through the links and around various mounting spots. The rad has some mounting holes in behind that you can take advantage of, but be creative for the most part. I also bent the screen around the rad where I could to "hug" it and keep it in place. If you want extra securuty, JB Weld would be a good help, but I didn't feel it was necessry. I tested my mounting job and it was good & secure. Don't forget to remove the duct tape when you're done LOL.
So in a nutshell...
(this is easiest with the lower fairings removed)
-Measure the rad
-Cut you screen to fit
-do a test fitting, trim where required etc
-remove screen, and paint it if you want
-duct-tape it in place while you work on the mounting points
-make sure there is nothing to interfere/damage the rad
-it's probably best to have a bit of a gap between the rad and the screen
Another tip...try to sand the edges of the screen, or bend them to make a rounded edge. If it moves a bit you dont want it to snag your horn wires, etc.
I hope that hepls, I don't think I left anythign out. It's really easy, I can't belive I ended up typing this much to describe the process LOL. If you have any more questions, just let me know. You could also use Zip-ties to connect everthing and mount it (probably better since there are no sharp edges) but I couldn't find any.
Also, I later foudn this on ebay...might give you a better idea, and be a better design that you could try to copy...or just buy it if you don't wanna mess around with it. Mine is very similar, but without the frame around the screen.
http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&category=34284&item=2415589339
Although, my job only costed me about $20 Candian (appx $12 us) for the screens, paint, and wire. And I've got tons of screen material left now too...now I can have a leaf-free gutter!