WTB - Crystal - 17.6mm x 21.0mm

I'm looking to replace a crystal on a watch which is as of yet unidentified.  The crystal is 17.6mm x 21.0mm.  The crystal is beveled.  There are two vertical bevels running from top to bottom on the crystal.  The watch may be a mix of parts, so if we can't match the bevel, that's not a dealbreaker.  At this point, I'd just like to locate a correctly sized alternative.  A decent picture of what I'm trying to replace is available here:

http://www.mybulova.com/watches/1941-unknown-5689

Thanks much!