DIY SL cable hole plug
 

Recently upgraded the shift lever, cable & housing on my Masi, with microshift marvo. Unlike shimano, there is no plug where the cable goes in. Should I care? Maybe a small sponge? fwiw, I do not chew gum :p

Those Shimano cable entry port covers are often missing, I wouldn't worry. Now if you take mud baths with your shifters, port plugs or not, they will be well worse off anyways. Or you might be able to do the Click and Clack method. Black tape over the engine warning light, or cable port in this case. Andy