GatherMate2 released a separate classic version of their popular addon that tracks gatherable nodes. GatherMate has always been my go-to addon for tracking nodes.
While not specifically stated, this addon does in fact work with WoW Classic. I've been using it since GatherMate2 was updated. I wish that the authors of GatherMate2 would build this into the core addon, but until then, this will do!
Enjoy and Happy Gathering!