Hi JB_DK, that's a fine looking project you've got there. With some good detail provided by the previous owner.
As far as I know the hatches are the same as Firefly hatches. I'm sure you could make these out of Plasticard for the hatch assembly and paper clips for the handles.

I found a couple of links that show a bit of the hatch detail.

I hope these help a bit.

http://news.webshots.com/photo/24674...63387170oxnNFg

http://www.fototime.com/ftweb/bin/ft.dll/pictures?ma=t&userid=561FFE6D1F9D41F1985C97FDF945C 99C&albumid=5A4D94930D1F4246878D0C46E24E4496&st=he &GUID={D9401B74-FA49-492C-9DF8-746114EE7069}&sent=stored

Just found this hatch pic in "Walk Around M4 Sherman". It's a great book for detail pic's of various Sherman types.