If you could post the measurements ( lengths of the various edges and dimensions at approx center of CP for length and width) making the template is the easy part. (but much more difficult without any measurements - ie. from the pic posted it is a bit under actual size as the button holes are not 81 pixels (1 1/8 " ) in diameter ( If resized to fit the button holes to size it seems the CP is about 19 1/2 inches in length at the back edge - but like I say hard to determine without a few measurements to go by)
Something close to this but without exact measurements it's hard to be exact -