Schefflera's species are great for Calumma parsonii ssp. I would recommend Schefflera arboricola for juveniles Calumma parsonii parsonii and Schefflera amate for adult Calumma parsonii parsonii.
I also recommend having a walk around your local nursery for non toxic plants that have got good sized circumfrance stems.
Best Regards
Jeremy A. Rich