So I know you probably are fond of your current bottle but just as a 'suggestion', I bought these bottles;
http://www.amazon.com/gp/product/B00...?ie=UTF8&psc=1
I ordered the 24 ounce, not the 21. Evidently, the 21 is intended for bottle cages. The 24 is not. It fits. And it fits well. But it is a bit of a squeeze. While I'm able to get it out while riding without too much difficulty; I don't think there's any way this bottle would self-eject. It's a 'snug fit'.
Food for thought. Maybe just a slightly-too-big water bottle with a snug fit is as good or better a solution than some sort of locking bottle cage.