Hi Bluemchem

I think the first thing you need to do is to obtain a roof opening vent (not Lourves). This should be wide enough to span two sections of glass, or near as dam it. You would then need to remove the glass from the roof where you are going to site the roof vent. Add a cross section of aluminium to reduce the size to suite the new opener by using an aluminium infill along the side. you would then need to get glass cut to size to fill in the gap at the bottom.

Now you can fit the auto roof vent.

I know what I have said is very basic in description, but the theory is right.

You may be able to get one to the size you want from one of the greenhouse manufacturers. Its worth the try. Had a quick look around. Check this site out:
Aluminium Greenhouse Accessories