Small diameter, flexible speaker cable under $200?

Maybe Kimber 4TC? The 4 is about half the size of the 8TC and sounds pretty good. Many strands without large shielding make it fairly flexible in my experience.

I'd second the Kimber suggestion above. If you need really long runs, then the cost could go above $200, in which case I'd recommend Kimber 4VS (essentially the same cable at 4TC, except it uses a polyvinyl insulation rather than Teflon). In a bookcase system, I seriously doubt that you will be able to detect any audible differences between 4TC and 4VS cable.

It looks like Mapleshade will be perfect for your application.

The Carolina Audio cables www.carolinaaudio.com forgive the photos on the sight.. are fantastic and replaced the much more a expensive and bulky Acoustic Zen Satori's in my system and also outperformed the 47Labs cable that I tried as well by quite a margin... Very flexible and easy to use.