Look at my post here:
http://www.landyzone.co.uk/lz/f7/defender-bodywork-rebuild-187304-5.html
49th post on the page shows the glass, 50th post talks about fitting it.
I paid £24 for two side windows and 2 rear windows in 6mm laminate.
The seals I had, but can be bought from online glazing supply firms, you need a sort of 1-2mm outer gap and a 5-7mm for the inner and a length of the relevant sealing strip. Also, buy the tool, I did mine with screwdrivers and fairy liquid and it was just a nightmare.
To make the template in cardboard I gave my glazier I taped it onto the back of the aperture, then used a marker to follow the line round the body panel. Once done you can then go round the outline about 5mm smaller than - assuming the web of your filler strip is 5mm, I would always suggest getting your glazing made to the smallest size the web will facilitate or it will just be a a nightmare to install the filler strip.
Another option is look up Agricultural & Plant Glazier - these guys will come out to you and do this job, they want about £200 though - mind you, seals, glass and his time, maybe not that bad.