Shimano Shifter Cable Entry Hole Plug

It's really easy to change the shifter cable on Shimano trigger shifters. All you have to do is take out the little plastic plug and you have a straight shot to pull out the old cable and feed in a new one. Then you just have to screw the plug back in, as soon as you find it. It was here a minute ago. Did it fall on the floor?
It's not that it's so expensive to buy a genuine Shimano replacement, it's just inconvenient. A trip to the LBS just for that? Or mail order and wait a week (and pay shi