Yes, there are no key blanks for S150 keys. The keys are pre-cut. I think they are stamped. The website states that the S150 keys (and S324's) are back ordered. I believe the keys are no longer made.
As such, one approach is to find a similar luggage key (or blank) via a locksmith to work as a S150 key. My S150 key is a simple shaped key made of .053" thick stamped steel. Making a duplicate key from sheet steel is another approach.