There have been 60 alternatives suggested to endosulfan at the Stockholm convention. But most of them do not fulfill the POP criteria.
There is no organic or less harmful chemicals which can be used instead of endosulfan.
Major reason being that endosulfan is a contact pesticide, so is less likely to enter the ecosystem while the most of the alternatives fall in the neonicotinides group which are systemic pesticides. Wherever Endosulfan has been substituted by more expensive alternatives like neonicotinoids it has resulted in elimination of honeybees as a result of Colony Collapse Disorders (CCD).
This is why Italy, inspite of banning, used endosulfan during the pest attack on hazelnut crops.
More importantly, all the alternatives suggested are patented products produced by the European Union. Farming becomes expensive as farmers will be forced to buy European patented product at much higher prices. Presently, farmers spend Rs.220 per litre for Endosulfan. If Endosulfan is replaced with Imidachloprid* (patented option touted as a replacement to Endosulfan) the pest control price will increase for these farmers to Rs.2000. Other alternatives thiamethoxam (@Rs.3200/litre) or Coregen (@ Rs.700/litre) will be expensive for poor farmers.