If you have the K-2006, you can not only replace bottles, you can buy oversize refill bottles. All the dropper bottles can be refilled by pushing the tip to the side with your thumb, pouring in fresh reagent, and popping the tip back in.

However, Taylor's DPD powder bottle has a molded in dessicant, so it's worth replacing the entire bottle. DPD powder is VERY moisture sensitive, so that's an important feature.