hmmm...that's a real problem....not!
Personally here's what I would do...
go here:
http://www.keys4classics.com/html/Datsun_early_ID.html
and see which series your lock is and if it falls into one of the catagories on the bottom right of the page...
it looks like there are only 3 different blanks that it could be....heck you could buy all 3 and it would still be cheaper than a locksmith!
or email him the codes and your info and vin, he should be able to get you hooked up!