If the base is still there just crimp the top where it starts to curl downward. Thats how mine is and it forces the oil throught the rocker shaft with a higher pressure.

If the feed part that sticks into the head is gone than you're out of luck until you get a replacement.

Mine went a 200'ish miles without the supply of oil to the rocker shaft before I bought it and decided to adjust the rockers. Amazingly it has NO grooves warn into it and some how the valley had plenty of oil (maybe splash from the valves/rods).

They're pretty tough!
~J