As near as I can tell, there are no direct equivalents for this type of steel-- the Cr content is somewhat higher than most of the typical Cr-Mo steel grades. However, there are any number of grades that can be hardened to similar levels, and therefore provide equivalent service. I would discuss this further with a suitable steel provider in South Africa, if that is where you need to purchase the steel. If you need the composition of 40CMD8, here it is:
C = 0.35-0.45
Si = 0.15-0.40
Mn = 1.35-1.65
Cr = 1.75-2.15
Mo = 0.15-0.30