This is the Dimon command I use. It correctly leaves the HEAD/BRIK files in the -gert_outdir. You may want to play around with the -GERT_Reco -gert_create_dataset commands and their location on the command.
Dimon -infile_pattern $sdir/'*.IMA' -dicom_org -gert_filename make.$ntask \
-save_file_list "${subject}.${ntask}.dicom.list" \
-gert_to3d_prefix "${subject}.${ntask}" -gert_outdir ${session} \
-GERT_Reco -gert_create_dataset -quit