The wonderful Revit Lookup utility has been updated by Autodesk. You can get the 2018 source code at https://github.com/jeremytammik/RevitLookup/releases/tag/2018.0.0.0
If you don’t want to deal with source code and just want to use the tool, here is an installer for the compiled & signed DLL ready, courtesy of Boost Your BIM – https://drive.google.com/file/d/182W00Mk5Hj1FMHAo-xVnoFYlJ_s2Swrw/view
Boost Your BIM 
Gracias
Automatic continuous integration builds of RevitLookup are now available at lookupbuilds.com:
https://github.com/jeremytammik/RevitLookup#builds
https://lookupbuilds.com
Cheers, Jeremy.