I've been eyeballing Creative Labs' D100/D200 for awhile, so I wrote Creative with the same question. Here's what they said:
Thank you for writing in to Creative.
I understand that you are looking for a Bluetooth speaker that you can separate as left and right.
With regards to your enquiry, If I got you correctly you can access the link below to check if this is the setup that you want.
Solution ID: 93051
How to Link One or More ZiiSound D5x Speakers to ZiiSound DSx Wireless Subwoofer
//support.creative.com/kb/ShowArticle.aspx?sid=93051 (you'll have to add the http: back in as the forum won't let me post links.)
$400 is a little more than I want to spend for something I will primarily use outdoors on the patio...