I have tried typing in Fallout New Vegas as well as the names of the DLCs but none show up in the search engine. Are they no longer available? I would like to purchase Dead Money and Old World Blues some time soon.

They are still available.
http://store.sonyentertainmentnetwork.com/#!/en-us/games/addons/fallout-new-vegas-old-world-blues/cid=UP1003-BLUS30500_00-FNVDLC3OLDWRLDBL
http://store.sonyentertainmentnetwork.com/#!/en-us/games/addons/fallout-new-vegas-dead-money/cid=UP1003-BLUS30500_00-FNVDLC1DEADMONEY

They are still on Xbox, so they should be on PS as well.