creating Apple ID without postcode

In a browser search/URL box, type 'what is the post code for [insert your location] and search for the post code.

Contact Apple ID Support for assistance.  See the Apple Support articles below for contact information.  

Apple ID - Official Apple Support.   -

Contact Apple for help with Apple ID account security - Apple Support.  *   (Link doesn’t always load)  

Get Support      -    Work through the screens to get a chat option. You may have to pick a slightly different problem.

Apple Support schedule phone call.   -

Apple on Twitter       

From the Apple Support article below. 

Without proof of your identity via security questions and other carefully selected criteria, Apple Support can't help you reset a password or perform any other actions on your account. These policies are audited and reviewed on a regular basis.

Security and your Apple ID - Apple Support.      *

What country are you in? AppleIDs are unavailable in some countries since Apple does not offer any services to use an AppleID with in those countries.

If you're being asked for information that doesn't exist where you live, it's likely you're trying to create an Apple ID in the wrong country.