If anyone else has this problem with water dripping from the sprayer button, don't waste your time trying to fix the o-ring seals inside the sprayer. The water is leaking from a micro-crack in the housing, upstream of the first seal in the trigger plunger. I know this because I first replaced the seals. When it still leaked, I removed the button, reassembled the plunger and hooked up the hose. The leak was then obvious, as it squirted through the housing and into my eyeball.
In retrospect, it was obvious: If the water made it past the first plunger seal, the path of least resistance would be through the sprayer, not through the second seal and into the button area. Soooo, here are my suggestions: 1) if the leak is around the threaded connection at the base of the sprayer, replace the o-ring on the threaded connector. 2) If the leak is through the spray holes, replace the o-rings on the trigger plunger. 3) If the leak is from the button area, call Delta, because the housing has a crack that you can't see. If your sprayer assembly is discontinued (because the faucet connector has changed), they may send a new faucet, but you may just need the spray head, as I did. Now I have a brand new faucet still in the box without a spray head, because the old faucet did not have to be removed. I just screwed the new spray head onto the old hose. Done.