microsoft[.]com/en-us/p/amazon-prime-video-for-windows/9p6rc76msmmj?irgwc=1&OCID=AID2000142_aff_7593_159229&tduid=%28ir__hzexuo1tuckftyvikk0sohzg232xnfzdh6sol9et00%29%287593%29%28159229%29%28%29%28UUwpUdUnU78425YYwYg%29&irclickid=_hzexuo1tuckftyvikk0sohzg232xnfzdh6sol9et00&activetab=pivot:overviewtab
The link above came from an article at Windows Central -- it's the Store's app page URL. It did not show up for me searching the store. The app has reportedly been in development for a few months, but no one has seen any notices or advertising. And while the app runs, signing into your Amazon acct. so far does not. I installed it assuming that I'd forget/lose the link etc. -- that way there's a better chance I'll remember to check to see if it's working later on.