Powerbank instead of Alkaline D batteries
The answer is that yes, you can. There's plenty of cheap step-down modules available on amazon, ebay etc, and while I'm certainly not a fan of their build quality, they might sure get the job done here. Make sure to not get one with a low current rating; I'm pretty sure the motor will draw more than 2 A.
The question whether you can do it without soldering: huh, possible, but unlikely, you still need to solve the whole electro-mechanical problem of how to connect things to the former 1.5 V battery contacts of your blower.