If you're like me you went through, beat the tar out of the Dead Money DLc, and then left with just a meager handful of Cloud Kiss, or Ghost sight. Then you got back to Vegas and found that you couldn't get back to the Siera Madre. If you're like me you shouted a few key words at that moment. But here's the good news: Elija's chemesrty set will produce a sample of Cloud Residue once every 24 hours. You need 25 science or so in order to make it. It's in the abandonded BoS bunker in the same room where you find the workbench and his robes.

Sweetness!

Figured that out before I even went to the Sierra Madre.

I'm pretty sure this is old news, but good for you finding it for yourself.

i didn't know so thanks.

You don't even need to begin the DLC to have the residue just have a science of 50 or boost up with chems and mags and you have a nice place to get non addictable and better night sight.