I just got home from a mini road trip delivering Datsun 1000 and Toyota Celica parts.
Along my travels I stopped in at the Datsun Museum.
While I was there Chris showed me these.
 

 
I thought I would post this up as it seems like a handy thing to own.
 
 
If anyone is interested in these they should contact Chris from Datsun Museum.com.
He has two left, new in the packet that I believe he would sell.
 
Ash.