You may try this photo irradiation approach.
This is a reaction I have done for many times.
For my reaction, 1g of diphenylsulfide requires about 20mg I2, 500mL DCM and a quartz flask.
The reaction is completed after 40W UVC bulbs irradiation for 3 hours.
Methyloxirane is an oxidizer to regenerate of I2, but I find out that it is not very important if I let the reaction done under air.