Nigel,
13 inch tall, 5 inch wide, looks a bout the same size as the one in the write-up when you compare the cap size. He makes mention of 10" being the drum size, so if you factor in between 2 or 3 inches for the cap, and the 1/2 inch thicker bottom side, this is what you're looking for.
Available at home depot, although it's not on their website, and you can no longer buy it online from any retailer.
Therefore, it has been discontinued and replaced with an electronically controlled valve unit.
http://www.geappliances.com/smartwater/model_fs.htm?GXWH04F
strotter
sorry for my quote of your post, I must not have been reading. the point about it failing in a crash is important and I overlooked it when quoting you.
apologies!