The sliding hatch is the one thats slides back and forth under the windshield.
The windsheild support can be had by the manufactor of the windsheild. If you look in the corner of one of your windows and you will see the name. *Mine is Water Bonnet and they are still in bussiness. I looked them up once but forgot now??
Never mind here is there link!!
http://www.waterbonnet.com/table1.htm
Drain holes have been talked about pleanty here and you can find using the search at top of page.
Bimi enclosure *to much for this poor fisherman!!