Power Steering Resovoir Cap

[Erantha]

I own a LN107 Double cab, a Toyota hilux SSR-X, My dad brought it down from Japan in 1994, it had done 18,000 Kilometers, and the manufacture year is 1992.

My power steering reservoir Cap just broke, the problem is the type of Cap i have, is no where to be found.

the cap which is available is like this

see the bottom part of that Cap is Flat. I am looking for a Cap which has like a rectangular beam, and has like a ball on the bottom. The pic of what the bottom part looks like is this

Please help me out, if anyone from Sri Lanka knows about where i can purchase this cap, because for about two weeks, I have been running putting powere steering liquid, once in two days, because the cap i have can't handle the pressure, please let me know as soon as you have an answer