Where to source Giant Accessories?
 

I just picked up a Giant Propel. It currently has a mechanical group. I'm considering switching it to Di2.
It's easy to find a Di2 group, but where can I buy the associated Giant specific covers/brackets/etc? Do I have to go through a Giant dealer or is there somewhere to buy outright?

Google is no help since any combination of "Giant Propel Electronic Di2 Cover Housing" just yields thousands of Propel reviews.