Shayne
I fabricated a new roof hatch my HUP, which I still need to install, to replace the badly bent one that I've still using after 30 years of fun with my HUP. The roof hatch itself is relatively easy to fabricate, it is all the latch hardware that is hard to come by. So if you find a bent or rusted hatch take a look at the hardware if that is useable grab it.
I'll dig out the drawings of the hatch and post them to my website. If you have not already seen my web site here is the link to the hatch information already posted.
http://www.canadianmilitarypattern.com/Posting.html there are a number of drawings of the hatch hardware also listed on the home page
http://www.canadianmilitarypattern.com/
Cheers Phil