It's in the PluginStore, made into an RBZ format download.
https://sketchucation.com/pluginstore?pln=surfacegen
It's not Thomthom's, it's Diggsey's plugin...
It'll probably still work in v2018 - however, because it's old and unsigned, you'll need to set the SketchUp Extension Manager's Loading Policy to "Unrestricted"...