How can I get enough Stingers for a Blade of Grass?

I'm look for a blade of grass to make the night's edge. I got all the jungle spores and eleven stinger, but the hornets, and big stingers stopped spawning. How can I get more stingers?

Assuming you're playing the PC version, as of 1.2, Hornets and Spiked Slimes will both drop stingers. I don't believe either one of them should have the potential to "stop spawning," unless something has impacted your Underground Jungle biome in such a way as to prevent normal creature spawning.

If you have any Corruption or Crimson that's interfering with your jungle, you should look into either counteracting it ASAP, or creating a new (properly protected) jungle elsewhere. You could also generate a new world and harvest its jungle, if you wanted to go that route.