I checked a local locksmith for my own '62 40. After 30 minutes of looking through books and making phone calls he found a source of key blanks. $8.00 each with a minimum order of 10. FWIW I think SOR is cheap in this case. I will be ordering my blanks from them.
Try finding an old timer locksmith in your area. The newer places just don't have the inventory of low-demand blanks.
The door locks for my 64 are on a "Dominion Lock Co. #TA12". The imprinting is well-worn, but it looks like it also says "Montreal, CAN". I had 2 made a few years ago for $12/pair. I brought in the code from the lock cylinder face and he looked the code up in the book. The original was too worn to copy.