My comment went way beyond the supply of glass.
There was a time that Amtrak had a whole fleet of domes as well. VIA decided theirs was an asset, even a national treasure. Amtrak decided they were trash. So over time, Amtrak allowed its domes to deteriorate to the point that they were indeed taken out of service.
So now Amtrak, and its conservative opposition, point to the current condition of Amtrak domes as justification for scrapping or selling them. If these were buildings that had been given official historical status, they would face an uphill battle to be demolished. In my opinion, domes are of historical value and could still be in regular service.
Canada got it right. While Amtrak still owns a few domes, the USA could get it right too.