Here is a reproduction of the plastic sprinke cap that you can purchase new, now:
http://www.gourmac.com/launsprin.html
But you can find the older ones on ebay too.
Or, take an waterbottle's plastic lid off, heat a nail and punch holes in it. Re-screw the lid on, and off you can sprinkle. Not as wonderful as the one Mom used.....but will work