Have you tried downloading the topic file using nimare.extract.fetch_neurosynth? Specifically, you should be able to use vocab="LDA50" and version="7" to download the most recent version of Neurosynth with the 50-topic model included as the features.
In order to faithfully reproduce the original meta-analyses, you would need to use a threshold of 0.05 instead of the default 0.001 in Dataset.get_studies_by_label(). I found that out for How to replicate Neurosynth meta-analysis in NiMARE? - #7 by tsalo.