hi,
you should be able to get the window seals from most good parts suppliers.
my local parts supplier is "john craddocks" in cannock. they are in most land rover magazines and are also on the net, just do a search.
i know they stock them as i was looking to change mine along with the rear sky lights too.
however be warned they are not cheap.
they actually advised me to use a silicon sealer and seal the windows from the eliments.
if i remember right you will be looking around £40 -£50 for both window seals.
i am putting off doing mine until i have my disco resprayed when the weather picks up.
hope this helps