Help with Crystal

I'm in the process of reviving my fathers A9 with 10BC inside and I need a new crystal. There is no case number inside. I searched the G-S catalog but couldn't find anything close. According to Bulova styles it's a Tonneau and the closest I can find is CMY or CMT. It measures 17mm across the top and bottom and is 20.5mm long with curved sides. Any help to locate one or where to look is appreciated.