The going price for a Durst AUDA70 piece of regular glass is approx $15 on ebay. There is a company in the USA http://www.fpointinc.com/ who supplies AN glass cut and beveled for way less than that price you were quoted. I made glassless inserts from a piece of sheet aluminum salvaged from some electronic equipment, it was the same thickness as the glass. All you need is a hacksaw, drill, file and patience.