LOV is an excellent source for finding and downloading vocabularies. Each vocabulary is available in the N3 format which Tropy supports. For example, here is the gn vocabulary.
Please note that sometimes vocabulary files also contain resources which are defined by other vocabularies. Tropy will always try to import everything in the file so sometimes you may import one file, but Tropy will add one full and multiple partial vocabularies (or, if the file contains some of the vocabularies included with Tropy by default, there may be a warning message about a 'locked' vocabulary) -- in such cases, don't worry: you can just delete the partial vocabs again (or just leave them and ignore them; they should not affect your use of Tropy in any way).