Do you have any glaziers near you, they will cut glass to any size you need and should be able to provide toughened safety glass, have a look at www.yell.com and search for any in your area. Alternatively I do know that Optimum sell glass shelves designed for hi-fi and TV's, you've probably heard of them but you can just buy the shelves on their own rather than having to buy the whole cabinet, it might work out quite expensive though. Their website is www.optimum2000.com
I live just outside Northampton. As it goes we are having a little prob with some glazed units on the house and I ran this past their cs person, she says they can supply glass made to measure in 6mm and 10mm (which optimum) also supply so I think I may be ok. So I am sending them the measurements today so that they can quote "me happy?" LOL!