The Myers Cooper still survives, according to these posts in the
Motorbike-powered race cars in Australia 1950 - 1980 thread:
Just to stir up the mind cells what is the history of the Jack Myers Cooper & where is it now, thanks to all for your inputs keep it going.
It is now with Andrew Halliday in Sydney, currently has a 500 JAP but he is building up a 1000 V twin for it, it certainly has had a chequered history originally being the car Jack Saywell raced in the early fifties and since then has had a multitude of owners including of course, Jack Myers.
Andrew Halliday and his family also have the ex Jack Brabham midget no. 28 and the Waye 500 which I think was mentioned earlier in this thread.
The Jack Myers Cooper was originally the Jack Saywell Mk 4. The line of ownership then went (I think) Bill Reynolds, Ron Williams. Jack Myers, Bob Joass, Peter McLeay, then Tony Caldersmith who did a big rebuild then sold it to Matt Segafredo who I think still has the car -- perhaps in Western Australia?
Edit: Oops! Dick beat me to it, and with better info.