While I cannot help you with a key blank, please allow me to share some advice based on personal experiences and first-hand testimony of others. Those switches have been known to create great turmoil and hardship, ...and likely the reason why they are not being manufactured any longer. There are several very good rebuilders of original type switches that I would suggest you consider exploring that option. One person I highly recommend is Dick Crabtree out of Pickstown, SD where you can purchase a completely restored pop-out complete with two keys for under $200.00. My thoughts are if you spend any length of time trying to find a correct key blank for your 'Made in Spain' switch, along with paying a locksmith to make the key, you are partially on your way to buying a restored original switch that will likely last you a long time. If your 'Made in Spain' switch decides to let you down sometime while you are driving, the stress & expense of getting you home might rival what you would have paid for the restored pop-out.
Aso, you did not mention your bodystyle however on certain models that have a keyed door handle, Dick can sometimes match the door and/or deck lid handle with the ignition switch key. Just food for thought.