I am not sure if this link will show up, but I did run into this on Ebay while checking out H3 stuff. It says it fits and is only 15" tall. I don't know if it works, but you asked for shorter...
http://cgi.ebay.com/ebaymotors/EuroSport-ANTENNA-Hummer...temZ7997567526QQrdZ1
By the way, if it does work...please let us all know.