I picked up a good tip from a DIY show for making templates...
Cut strips of cardboard - length of each depends on the radius you're making the template for - butt the pieces up against your object (around the edge of the monitor) and tape them together one at a time.
Now you have a master template, lay it onto either a permanent template material (ie: thin mdf) or directly onto what you want to cut and trace around the edge (the inside edge in this case).
You'll need to smooth out the curves a little, because tracing around the cardboard strips will have given it a polygon look.
Finally, it's time to carefully cut out your material and amaze yourself with a perfect fitting bezel!
Steve