I used one of the many available on the internets. The first hit on the Googles in one that prints on A4 paper - this will create a template that is slightly smaller than what you want, with the A4->Letter conversion. I am sure there is a Letter sized (8 1/2x1 ugh!) template somewhere.
I believe that there is a fair amount of play though.. the pads on the SIM card are pretty big.. they can handle a slight misalignment and not bork out.