Brendan, I already got a whole bunch of sensor sockets from AliExpress.
These ones. Unsure of the material...
I am not sure how to check if it is beryllium copper... any ideas?
Also I just noticed that Altronics is (mainly) Perth based, 3 out of 6 stores are in Perth. I could get the connectors for all of us and send them with the rest of the parts to you. I can get discount with our trade account and if don't have a local shop you could also save few $ on shipping.