A cheap way out is rain gutter screen, in the US a 10' roll is less than $6 for sparkly aluminum. When it looks crap just cut off another piece. One roll should last for a few years even in your climate (repaint your rad in black before attaching). Fold over the ends of the radiator and attach with the side cover screws.
This has worked very well at keeping gravel and rocks off the rad fins, and cuts way down on bugs.
If you want something fancy, eBay has heavy SS covers on all the time, both for curvys and pointies.