Like all things with Cisco these days you need a smartnet contract with them for the products/software you want to download/use.
Without this, you are not "entitled" to use the software. I do frown on Cisco for making it more challenging for us individuals that pay good money for their material and exams to be able to get a hold of images and software for lab purposes. I mean even Cisco ISE gives you 60 days eval. Why is it so hard to do this for things like SDWAN?
That being said if you have a good relationship with your Cisco Account team they might be able to help you out with getting these images.