Stuff gets discontinued. It's the name of the game. Especially when something better comes along.
I get customers that call constantly for Nav updates for their Porsche Nav systems. Porsche only holds updates for a couple of years at best then the next system comes along and the drop the old one. I would be money that the other manufactures do the same thing.
If you can't get one from Honda your best bet might be to find someone selling a used one. eBay perhaps?