You may additionally try the treatment in Flore générale de l'Indo-Chine: http://biodiversitylibrary.org/page/31182716 This is outdated anyway and unfortunately, the supplement volume, published in 1945, is not available online. But the same author, M.-L. Tardieu-Blot, has published all the new species of that treatment in Notulae systematicae in 1944: http://biodiversitylibrary.org/page/7332775 Both publications are in French. At least this will give some guidance, which species may be considered in addition to the Flora of China treatment. You will be able to see some of the type collections using the following search form: http://science.mnhn.fr/institution/mnhn/collection/p/item/search/form The Muséum national d'histoire naturelle in Paris has scanned big parts of their collections and made accessible by this way.
I don't think it is I. campanulata. I. campanulata is known from Western Ghats and there is almost no one common species between Western Ghats and NE India.
I have got a plant that was collected from North Vietnam. It looks very like I. omeiana, but am told it's a new species. Is it the same as yours? Two pictures attached.