Hi Bill
You are not the first person to need a new hatch as the removal of this source of roof leaks was a common post war modification.
Your also not the first person to ask for details to figure out just what it is they are looking for, so here is a link to a page on my CMP web page showing some details of the hatch as seen on 1945 HUP.
http://canadianmilitarypattern.com/H...f%20Detail.htm
Cheers Phil