thanks all. i ordered one of these, it should work nicely

http://www.jegs.com/i/JEGS-Performance-Products/555/511035/10002/-1

Further reference. Factory parts manual schematic:

Thanks for those Alan!

That jegs link is pretty much what i ordered.  If you look closely the mounting tabs are in the center of the unit, not the edges.  To squeeze it between the radiator tabs i used some basic standoffs.. I am extremely happy with the results

Alan,

On what years would those bottles have been used?

Those bottles would have been used on 1970 - 1973 model years.

10 hours ago, Patcon said:

Alan,

On what years would those bottles have been used?

1969, 1970, 1971, 1972, 1973 production years. S20-engined models only.

It's fascinating that they only did that on select models and didn't feel the need for it on the rest of the line

On 11/9/2016 at 0:18 AM, HS30-H said:

For reference, factory PS30 'Fairlady Z432'/PS30-SB 'Fairlady Z432-R' type coolant overflow bottle and mounting bracket:

Alan, any chance these are still available in Japan or elsewhere?

Mike

3 hours ago, Mike said:

Alan, any chance these are still available in Japan or elsewhere?

Mike

These are very hard to come by, Mike. It took me a few years to find the one in my photos...

Your best bet would be Yahoo Japan auctions, but they usually change hands for $$$$. If strict originality is not important then you might be able to find a similar setup (slightly different mounting bracket) on a full size sedan of a similar age, like a 130-series Cedric for example.

A slightly left-field suggestion would be to look at the setup on a Triumph Stag (no, really...). A fairly similar bottle with a mounting bracket that can be modified to make it bolt into the same pre-drilled holes on the front of the radiator core support that the PS30/PS30-SB overflow bottle fits. Still available new from the major British car parts suppliers like Moss Motors. Just don't tell anyone where it came from...   

Thanks Alan!

funny how a simple (to me) question, opens up so many answers