A while ago during the brass shortage we had new hires out of uniform compliance because the company couldn't acquire enough wings and hat pins. And that was ok and everyone knew about it because it wasn't like these pilots wanted to be out of compliance, but the literally couldn't get the required items. I'd say in your case the company, this time by their own choosing, is not providing you the full uniform complement. That is their prerogative, and honestly it does make sense for them to not buy you a blazer you won't even be able to wear this fall when the new one comes out. But because you have not yet been provided a full uniform I would wear whatever you darn well please when you encounter cold and/or rainy destinations. And if anyone wants to call you out on that, I would just simply explain your situation and move on. If it's October, and you have not been provided a blazer, and it's 20 degrees somewhere, no one expects you to just suck it up in the short sleeve shirt. Be safe. Be comfortable. The company made this decision for you so I wouldn't think twice about wearing a Northface jacket or other professional-looking outer wear until the company provides you with the complete uniform complement.