Size and material of O-ring replacement for Inon Strobes

I need to change the o-rings of battery box of an Inon S2000 strobe. This model have the same size of Inon underwater strobes models Z-240, S2000, D-2000, D-180 and Z-220.

Do you know what size the o-rings have, what o-ring material (NBR - Nitrile, EDPM, etc) and what hardness (70-Shore, 80-Shore, 90-Shore, etc) would be necessary? 

Thanks

I have measured with a caliper and these seem to be the measurements. I just need to know the material and the hardness. It looks like a rather soft silicone.

Inside Diameter (ID): 41.5mm
Cross Section (CS): 3mm