Glass shops worth their salt should be able to get low-iron aka Starphire ("Starphire" is a brand name IIRC, there may be other brands who make low-iron glass as well). At least .. what I can tell you is I've dealt with Glass Guild in the past, and noticed that they can sell Starphire.
But yeah BVA can also set you up with glass.
They might have a spare piece lying around .. or two.